I (M23) think I've changed sexual orientation. How do I tell my boyfriend (M20) of 1 year and do we have to break up?

I think I already know what I have to do but I'm really dreading the answer.

This is my first relationship, and I've been together with my boyfriend for just over a year, our anniversary has just passed, and so far everything has been going really well. We are a perfect match for each other romantically and we have almost no problems except for in the bedroom, where I just feel like I can't do it. I used to dread going to see him in case he was expecting something sexual because it felt so wrong for me, but I discussed that with him and that's been off the table for a while now, although at the time I thought that was just a case of 'being ready'. In any case, sex is a normal part of a healthy relationship and I can't keep denying him that because I know how much he wants it.

I've had the feeling for a while now (maybe a couple of months) that I might actually be straight, I'm not completely certain but I have sort of a gut feeling. I thought that maybe it was a phase, or that with some time and effort I could change, but so far that's been in vain. Obviously relationships take effort to make work, and considering how compatible we are and how great of a relationship this has been I don't want to just throw everything away for one little thing if it just comes down to attraction.

I feel like I really love him, I love him very deeply. I love spending time together, I love his presence, I love everything about him, it's just that I don't feel that intrinsic attraction. I spend almost all of my free time with him every day, and the truth is he's really my only friend, I don't know many other people. Before I met him I didn't have any friends for a long time, and I was so lonely, so I'm lucky to have him in my life.

On the other hand, it would hurt both of us more to carry on in a relationship that truely can't work, and I feel that I can't just carry on for the sake of it because it will all end up worse. I'm starting to feel exhausted living a lie and keeping it all to myself, and I feel so evil for lying to him too.

He seems quite obsessed with me; he sends me romantic messages and reels all day long and very often talks about spending our whole lives together and being in it for the long term. I just don't want to break his heart or hurt him in any way, if I broke up with him it would shatter his reality and I worry about leaving him with a permanent psychological scar, or even that he might hurt himself (although he's never indicated that he would do something like that). It would be so difficult after already being together for a year, I can't just waste his time like that. I feel so guilty for it either way.

I don't want to leave him either, I need him and I can't imagine my life without him. He is a pillar in my life. I don't want to be lonely again, I just couldn't bear it. At the same time I know it would be selfish to keep him in my life just to keep me happy. In my ideal world we would just be best friends but after breaking his heart I could imagine he wouldn't want to talk to me again, or at the very least he would need time to heal and I understand that. The choise of whether we get to be friends after is down to him as much as me, so it's not a decision I could make for him.

I just don't know what to do at this point. I doubt I will ever find another person in the whole world who is as kind, pure souled, and compatible as he is. And what if I break up with him and realise I was gay all along and come to regret it? Even if I decided to break up with him I don't feel I have the emotional strength or the will to do it, I just couldn't bring myself to do it.

I am already going to speak with a therapist about this soon, but I thought I'd get a wider opinion on this too, because I don't know what to do. Any advice is greatly appreciated and thank you very much for reading all this.