I am sure she’s aware that marriage doesn’t make people unhappy, but it’s hard to deny that people learn what they live. And when you’ve lived through a bad parental marriage it’s not a stretch to think that, if you’re not careful, any marriage you create, no matter how initially healthy, may transform into the format you grew up with.
I think this is what people are really saying when they are marriage shy due to having grown up with divorce.
Lots of really good advice so far.
I’ll hit on what’s standing out to me. I could be totally wrong, but I’m getting a different vibe from what you’re saying.
To be specific - you sound to me like you don’t have anything against kids. You sound like you have a massive problem with “being a housewife.” The two aren’t the same thing. If you don’t like housework and don’t want to be domestic, that doesn’t mean you can’t procreate. It just means you need to lay the groundwork down now, and set expectations appropriately from the start. (And that means for YOURSELF as well as for your eventual mate if you marry. If you work out what you’ve *specifically *got against that whole concept of “housewife”, then it will be easier for you to determine what you need to do to make that specific situation not apply to your life.)
Here’s some ideas:
“Honey, we make enough money to hire help to keep the house up. If you don’t want to spend it - I will - I’m not a Holly Homemaker, sorry!” 
“Honey, I’m really not into cooking. If you want homecooked meals, I’ll be glad to pick some up from some really good caterers, or I’ll totally cheer you on while you work in the kitchen, but I’m not cooking.” (I told my husband this from the start - I’ve perhaps cooked a dozen times in over 7 years together, and all were because I wanted to “mess” around in the kitchen. A few of them were actually edible.)
“Honey, we make enough money to hire a surrogate parent. I don’t have enough seniority in the company to take the time off for pregnancy and breastfeeding, and I want the best for our eventual kid.” (this is extreme, but totally possible)
“Honey, we make enough money to have a fantastic au pair for Junior/Junioress. I’m not really into this mothering crap, so we need someone nurturing for the kid.”
It almost sounds to me like you might be partially blaming your birth on helping stress out your parents’ marriage (“way too young when they had me”) and that you’re projecting that fear onto an eventual kid for yourself. You’re a lot older than your parents are - you sound like you’ve got your financial ship in order, and all you need now is some really serious planning conversations with your honey to see if you can work out to being on the same page.
Your boyfriend can’t see inside your mind, and he may not realize that you’re totally against the idea of being a typical “womanly” (god I hate that term) caretaker homemaker, motherly person.
That’s fine, but **you **have to be really damn clear that this is non-negotiable. He may be hoping that after you two wed, he’ll have someone to iron his pants and wash his socks. It’s only fair to warn him that ain’t gonna happen regardless of the kids/no kids situation.
Now, I could be totally off-base on this, but that’s what I’m sensing from here.
To address the idea that living together is just the same as being married, and getting married doesn’t change anything, in my experience, it does. Knowing that the two of you made a commitment to each other, you made all the plans and paid all the money for a wedding, you stood up before your friends and family and made vows to each other, that all means something.
I don’t understand this. I would not wish to marry a lazy addict. A FORMER lazy addict who “overcame obstacles,” got his life together, cleaned up his act, and has now been hardworking and sober for several years? Sounds like a genuine catch to me.
Yup. No problems with that one.
If I read this correctly, you are saying “it sounds as if the OP’s mother isn’t all that enthusiastic about the potential fiance. Therefore, if the OP goes ahead and gets married and later there are marital difficulties, mom will not be a good source of emotional support.” First of all, you don’t have anywhere near enough data to make either of those assumptions. Secondly, “my parents would or would not be kind to me if I ever have marital trouble” seems like an exceedingly odd thing to give much weight to in deciding whether or not to marry someone. Seems to me that questions like: Do I love him? Do I want to spend the rest of my life with him? Do I want to get married at all, or would I rather stay single for the rest of my life? should be the OP’s focus.
On the contrary, it may very well simply show that he knows what he wants from life and he is willing to make the hard choices necessary to be sure he finds it.
If a woman is dating a guy and finds out he isn’t interested in marrying her, but what SHE wants out of life is a stable marriage, most of us would advise her to dump him and find a guy who shares her life plans, instead of wasting valuable years with a relationship that’s not going anywhere. Why should the OP’s boyfriend be any different?
The point is: does she like who he is now? Would she love and admire him if he did *not *have a shaky past? Too many young women (and they tend to be younger than the OP, but not always) give Bad Boys some sort of relationship “credit” if they’ve faced rough patches in the past. A past filled with addiction and anger issues can sometimes be used to rationalize current bad behavior, under the idea that, “but he’s come so far!”
I think one should give people *some *credit for bettering themselves, but that credit should not be extended so far that it becomes the reason to stay with a guy (or girl) who you actually don’t like much and wish would change some more.
(…says the voice of experience…)
I had the same concern after the OP, but after the additional information, that part doesn’t worry me so much. Sounds like this is mostly the OP’s “issues”, which is actually great, because if she wants to, she can work through them! It’s so much easier to fix your own issues than to fix someone else’s!
This is true. You are shacked up. Unless you have legal reasons to pursue marriage, why now? I’m happily married, and glad for it because it turns out we needed to be married to adopt - but that isn’t in your picture. At some point you may want to be married, but I’d want to know why he wants this now?
On the other hand, you are happily shacked up - after two years getting divorced and breaking up with someone you are living with are pretty much the same - just more paperwork if you get divorced. So, why the reluctance?
I suspect this kid thing is driving both his asking and your reluctance…
My mother in law spent twenty years living with her boyfriend before she married him - in her sixties - for the reason college students get married - she wanted onto his insurance. 
There is the old adage from rich folks that if you have to ask what it costs, you probably can’t afford it.
The fact that you are still wondering about the answer speaks volumes.
I think it is a given you are not 100% ready for marriage - maybe you are 75% ready? 82% ready? 55% ready?
The point is, until you can say you are 100% ready and happy to make such a commitment, leads me to think you just can’t afford to say yes just yet.
BTW, to those who are/were married, how many of you had a “surprise” proposal versus those of you who sort of always knew it was a given and you were both just waiting for the right time? Maybe you were surprised by the moment or the violinist suddenly popping up at the restaurant, but my guess is the concept of marriage didn’t spring out of the blue, did it?
I ask because it seems odd that someone would be “surprised” by a marriage proposal.
You’re certainly right, at least in my case. I went so far as to actually ask my girlfriend, “If I were to ask you to marry me, would you consider it seriously?” She replied, “I wouldn’t just consider it, I would say yes!”
Two weeks later I officially proposed.
I had surprise proposals, but never got engaged as a result.
Okay - I don’t know whether that analysis works for the OP or Czarcasm, but it seems sensible to me.