Becca, I wonder that all the time. My SO has a successful career that's taking him places and his ex was working on her master's in biology as well as some other things. I don't do anything that I feel can compete with that.

So what I try to tell myself is that it isn't a competition. We are fundamentally different people, and while he may have been attracted by a couple of similar qualities... well, we've been together for six years and he's been with me both unmedicated and not. So I feel if he was going to leave me, he probably would have done it.

That isn't to say I don't beat myself up about it though. I have the exact same question in my head more than I'd like to admit. So you have my sympathy and understanding. If he's reassuring you that you are the one for him, try as hard as you can to believe it, and to tell yourself that the evidence is in your favor. Wishing you well.