Newspaper stories about things like “Woman beaten by 55-year-old boyfriend” just sound so weird to me: I wouldn’t consider a guy like that either a boy or a friend.
“Significant Other” just sounds euphemistic.
So does “partner”–sounds like a business arrangement.
But, there is no wholly satisfactory term, at least in English. “Person I’m dating”? “Sweet baboo”? “Better half”? “Worse half”? “Person I reciprocally have the hots for”? “Main squeeze”?
My…um…person-of-the-opposite-sex-that-I-live-with-and-plan- on-living-with-for-a-very-long-time-although-we-don’t-plan-on-getting-married, are grappling with this semantic issue on a fairly regular basis. Bf/gf just didn’t seem to convey the sense of permanance that our relationship has (we’ve exchanged rings and everything.) But we don’t want to marry so we don’t want to refer to each other as husband and wife. I kind of like calling him my paramour but he’d prefer I not use that around his mom 
Online I use SO because it’s short to type and defines it pretty clearly. Around friends I use paramour, boy toy, live in lover… But around new people or those who might not be so keen on my sense of humor, I just call him my partner.
In my eyes, if not the eyes of the law, that makes you married. Assuming, of course, you aren’t talking about friendship rings or something out of a gumball machine. 
But, call each other whatever makes you happy.
Nope, that doesn’t make us married. And common law marriage does not apply unless you refer to yourselves as married, and we don’t. We are committed to each other and plan on spending our lives together but we don’t want to get married–there just isn’t a good word for that yet.