My boyfriend is asexual.

We have been dating for 4 years and I really am in love with this man. Im pretty sure he loves me the same too. When we first started dating we were both virgins and he didn't know he was asexual, actually I was more worried about me not liking sex once we try it. He had a masturbation addiction and he used to say he does like the sex we have but he just cant fully enjoy it because he was too used to masturbating. Slowly him saying 'i do enjoy it' turned into 'I guess I'm just not into sex' and ended up with him saying he was asexual. This happened multiple times. He told me he was asexual and when I got sad about the lack of sex life he told me maybe he wasnt asexual and he actually enjoyed it, just to tell me he doesn't, and he is in fact asexual once again. He always tells me how beautiful I am and how much he loves my body and I know he isn't cheating or anything we talk to each other almost all day and he always lets me know where he is. I really love him, I want to marry him in the future and almost everything in our relationship other than sex life is going great but I just can't be okay with this. I do support him and tell him he shouldn't force himself to do something if he doesn't want to (he says he can fake enjoying sex for me) but this whole thing makes me feel so unattractive and also makes me mad. I get that he couldn't have known before we started dating but I hate that he told me he enjoyed it at first. I feel like it's my fault and i did something wrong. I feel like our sex life is salvageable but I'm just not good enough to find the solution. Breaking up is not a solution for me, I love this man. But i just don't know what to do anymore I feel so depressed.