Why don’t I want to have sex with my bf?

So my boyfriend and I are both 20 and we have been together for 2 years. I’d say the past 6 months my sex drive has literally gone out the window. I’m still attracted to my bf of course and we used to have sex all the time but I just don’t want to have sex anymore.

I have had very traumatic experiences in the past and he knows all about it but I don’t understand why it would affect me now.

I have talked to my bf about how I’m feeling and I have been quite open with him and he says he understands and it’s ok. On the occasion we will have sex but I do it for him, I don’t really get anything out of it but I don’t really care.

But recently we haven’t had sex in weeks and twice now during the night he has told his he is super horny and his dick hurts and keeps asking me to do stuff. I don’t know why but it makes me really uncomfortable but I haven’t spoken to him yet because I feel like it’s my fault.

Anyone know what I should do? Why this could be happening? Or any advise?