HIFW I can't figure out my current feelings about my 2.5 year-long relationship

Sorry for the long read, but here's basically what's going on:

I love my boyfriend. I care about him a lot and I want him to be happy. However, I'm not always happy when I'm with him because I don't think I've been able to be completely open with him emotionally in a while.

I've been dealing with anxiety and depression for about 5 years now but it peaked last year due to my birth control, and he wasn't the most supportive. He gets that depression isn't something you just stop, but I don't think he gets just how hard it is to break the cycle of negative thinking. He got extremely frustrated with me like two or three times during that period (twice we got into fights about it, which only made it a lot worse), and it made me feel like shit. I tried to be the bigger person and cut him a little bit of slack. He knows that what he did wasn't cool, but I've been where he was in that situation before this happened to me, and I understand just how frustrating it can be to be around someone that's always as negative as I was during that period.

He also has a tendency to be nit-picky with people in conversation. I've always been sensitive, and that started getting to me last August because I felt that he was being rude, disrespectful, condescending, and undermining my feelings. We've had a bunch of talks about it since then, but it didn't seem to click until about a month and a half ago when it caused a fight and I ended up having a complete breakdown, sobbed, and told him I "seriously [couldn't] take it anymore," and that I didn't know what to do anymore. He FINALLY seems to get that over time it has grown to upset me and that it would make me really tense in conversation, and over the past like two months he's gotten a LOT better about it, and he doesn't really do that to me anymore. It's really great!

Although the nit-picking has pretty much ceased (aside from us being playful and picking on each other), I still find myself feeling tense when we talk, as though it's a habit. I've always been sensitive, and the nit-picking combined with how he reacted those few times during that peak depression has just made me more sensitive and nervous. Like I said before, he's been really great since it finally clicked in his brain that it wasn't cool, but now I can't seem to chill out. I know this isn't a good thing in a relationship, and I think it's gonna take some time for me to feel fully comfortable...but I'm really struggling with it. I'm realizing now that I kinda distanced myself from him a little bit for a while without really meaning to, and now I'm just kind of...noticing it. I don't really know how to handle it.

I really want to talk to him about this whole thing, but just thinking about it makes my palms sweat because I know it's probably gonna make him feel pretty bad (which I hate doing)...but I want everything to be good. I've had thoughts in the past about breaking up over this, but I really DON'T want to. I really love him a lot and I think if we could figure this out we might have a good future together. I'm just kinda all over emotionally because I don't want to feel distance between me and him, nor do I want to feel tense around him. There's still plenty of good in our relationship that isn't mentioned here (this is just kind of a highlight reel of the worst stuff), but this stuff (and my pessimism) has obviously affected me enough to give me doubts, so it's kinda hard to figure everything out.

TL;DR: my boyfriend and I have had some issues in the past that have caused me to become kind of tense around him and subconsciously distance myself from him, and now that he's been treating me a lot better I'm having trouble opening myself up completely and chilling out around him. I really want to work everything out but my feelings are all over the place.

How do I bring this up, trolls? :(

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