Sex issues

So the past few times of sex with my boyfriend (26) I'm 19 female, he ends up going soft or isn't able to finish. Which isn't a problem like sex isn't everything but it still makes me feel self conscious. I'm very attracted to him so TMI end up very wet and turned on. He says he can't feel anything or his tip starts feeling weird so we changed positions and in everything we tried it's the same. What is going on? He says it's him and his brain but I can't help but feel like it's me. Maybe he isn't as attracted to me anymore? I don't know. Does anyone know what is happening and what to do to help prevent this issue. Thank you x