I was in the mattress business up until last fall, so for what it is worth…
Wow, that got long, fast. Executive summary…
A topper probably isn’t going to work. Check the mattress and if you see a body impression over 2 inches the mattress is likely dead. If no depressions, a thick topper with cooling tech might help.
If you were in my store, I’d steer you towards a medium to soft mattress and an adjustable base. With the right sale, you should find something that works for $1200-1500.
Toppers are just a bandage. Look at your mattress and see if there are dips and depressions greater then about 2 inches (1 inch if a foam mattress). (Why those numbers? That is where, if the mattress is under warranty, the depressions are deep enough to require warranty replacement.) If there are depressions then the mattress structure itself is not supporting you properly and a topper isn’t going to do much good because they don’t fix the underlying issues with the coil pack.
If you have to go that route, I’d go with 2-3 inch thick memory foam and make sure it has a cooling top (either moisture wicking or one with what’s called phase change material (PCM)).
Since you are curvy and a side-sleeper, you’ll want a medium to softer mattress over all. Too firm and you’ll find all the pressure on the hips and shoulder as you described.
For your situation, I’d recommend shopping for either an all foam mattress or a quality hybrid mattress. The hybrid is often a good compromise that is less expensive then an all foam mattress. Hybrids use a traditional coil base for support with a deep layer of foam on top for pressure relief. Since coils are a very mature technology, you get comfort similar to an all foam mattress but at about two-thirds the price.
I’d also recommend an adjustable base that lifts your head and feet.
I have a friend with sciatic symptoms and she found that a bed that lets her lift her feet up at night significantly reduced the discomfort. Consider an adjustable base (they can be found for under $1000) and it will make any mattress (even a very inexpensive one) feel more comfortable.
Most retailers are offering a free adjustable base with mattress purchase now, especially over holiday sales periods. The free base usually raises just your head. However, they will discount the entire selection of bases by about $500 (the cost of the head only one) so you can get a basic head and foot base for about $500 during those sales.
If you are buxom, I have had several reports (customers will tell you everything) that having your head up at night can keep the girls from trying to smother you in your sleep.
You can get the mattress at a store or online. Granted, as a former retailer, I am biased to the store route but there’s a reason stores might have 40 mattresses on display. One-size most certainly does not fit all. I’d also recommend reading The War to Sell you a Mattress is an Internet Nightmare
Ask about clearance pieces and returns. Returns should be mattresses that went to someones house. The customer slept on it for the trial period (anywhere from 30-120 days depending on who you are dealing with) and decided they didn’t like it for whatever reason. Returns are often sold without a manufacturer’s warranty (aftermarket warranties are sometimes available) and cannot be returned.
The mattresses are sanitized prior to resale and you can get them extremely cheap. For example, one of our very high-end mattresses might have a price brand new of about $4000 with an associated cost to the rep of about $2500. However, once it was returned, it hit the clearance side and the cost went to about $800 and we would sell it at $1000 if that’s what it took to get it out of the store.
Good way to get a high end mattress for a modest price as long as you can find something you like. (And while clearance pieces are technically not returnable, we’d often let you swap for something at the same price or more.)
My mattress set-up is an all foam mattress by Dormeo I bought off clearance with a head and foot adjustable base with massage (vibration). I was a side sleeper and it took about 3 weeks to adjust to sleeping all night on my back. With a good foam mattress under you, you don’t get the pressure and I sleep through the night with my head and feet raised and no urge to turnover. (The cat certainly appreciates the lack of movement.)
Other advantages I have found is that during allergy season I can set myself at a comfortable level to help with drainage and the massage is great for those days when my whole body was aching from the flu.
Lastly, in a store setting, do not be afraid to negotiate and ask for free stuff. On average, I’d say the mattresses and bases have about a 40% mark-up in them. A lot of accessories are marked up even higher. Ask for discounts or bundle pricing. Take advantage of the no interest financing if you can.
You are not going to insult the sales rep by making an offer as long as you know you want that mattress and will do the deal if we agree. Most reps are nice people, although there are a few sharks, but they all have quotas to meet and want to you to be happy with your purchase. Work with them and they’ll find you the best deal in your budget.