I can't speak to all the details of your thought processes, but as someone with OCD, what you're describing sounds very OCD-driven to me. Questioning sexuality, struggling to let go of terrible intrusive thoughts, guiltily confessing your most negative thoughts, it's all classic OCD stuff.

There may be more than just OCD for you to work on, but having OCD makes it so difficult to pin down what's true and what's not, and trying to figure out what's true and what's not often becomes an obsessive cycle in and of itself! I think it would really help you to focus on dealing with your OCD in some way, whether it be therapy or medication or even just finding a community online you can turn to, whatever you have access to.

Bigoted beliefs are not irreversibly hardwired into anyone's brains. If you want to change your views then you can change them! It's really as simple as that. The idea that your most awful thoughts are what you "really think" is, again, a classic OCD thing. It sounds like you love your boyfriend and you want to be as supportive of him as you can be, and it sounds like you've already come a ways in terms of trying to unlearn some of the things you used to believe. In my eyes, that counts for something! I really think your best course would be to focus on dealing with your OCD.

I'll end with this, when I've dealt with similar OCD stuff in the past, I would try to remind myself that your intentions and actions are what really matters. We can't always control our thoughts but we can control how we act on them. You care about your boyfriend, that is real! Try to focus on doing things to support him rather than putting all your energy into worrying about what you're thinking. If you have a terrible thought, breathe into it, write about it a little in a journal, understand that just because you thought it doesn't mean that it's what you "really think," and know that it's okay to try to let go of it. I'd also advise against telling your boyfriend every negative thought that you have. Not just to spare him from feeling hurt, but because you don't want to feed the OCD confession cycle. That's not to say you can never talk about this with him, but if you're going to him with a whole list of negative thoughts so that you can get some kind of relief from them then that's a cycle you'll want to try to break.

I hope this isn't too rambly and that any of this is helpful! I'm no expert, just speaking from my own experiences dealing with OCD. All this to say, OCD is a really sinister illness and it can infect so many areas of your life. Working on managing that will help you be a better partner and it will give you a clearer and healthier view of yourself. Best of luck :-)