Not enjoying sex - am I the problem?

My BF 36M and I 31F have been together for over a year now, but good sex hasn’t been our strongest suite. In my past relationships I used to want sex and enjoy it a lot, but I have never really enjoyed sex with him, I have tried to be vocal with him multiple times but it hasn’t really changed, he’s been very receptive and wants to change and please me but he is not able to make me orgasm. Because of this, I feel like I’ve given up on having sex with him, it’s almost like I don’t want sex anymore, I’ve tried to picture myself with a hot celebrity but it’s almost like nothing turns me on. I know that he wants sex, and I always say no to him and I feel very guilty because he isn’t asking for too much.

Side note : due to some personal reasons like health and work, I’ve been very stressed for a the past few months (unfortunately it’s not going to get better anytime soon, it will take time). I don’t know if this has also contributed to my low sex drive. My BF has been such a rock solid supporter through all this, I wouldn’t have been able to do it without him, we love each other a lot. I do want sex but it’s not the top priority for me right now, I’m hoping that my sex drive gets better. But I constantly feel very guilty that I’m not giving him what he wants. He’s been understanding but there’s only so much a person can take and I don’t know what to do. I really love him a lot and I know he loves me but don’t want to lose him for this!

Any advice for us? Thanks in advance!