Depression and sex (TW? TMI?)

I’ve been in my relationship for coming up to three years now, and our experience of sex has been a bit of a rollercoaster. When we first got together (me 15 him 16) my boyfriend really wanted to have sex and have our first time together etc. At that point I felt a very strong aversion to sex and even kissing and thought I’d never want it, and this difference between us caused some difficulty and insecurities (mostly on my part). After three months we had our first kiss and by six months had had sex. It took me a while to feel safe and secure enough but it was good and we would do it fairly regularly (classic teenagers). Fast forward to now (me 18 him 19) and my depression (undiagnosed and unmedicated but i’ve had some therapy) has been causing my feelings towards sex to change again over the last few months. We’ve been lucky and have been living together near his family’s house, so have been together pretty much all day every day for a while now. Recently I just haven’t been feeling that interested in sex, but my boyfriend still wants to do it fairly regularly, although not as often as before. I never really feel that into it and I’m never sure at the start but kind of just let it happen because I ask want to please my boyfriend. I either don’t enjoy it and feel stupid afterwards, or if I start to enjoy it I feel incredibly guilty and confused. I don’t know how to talk to my boyfriend about it, he kind of understands that I’m not that interested anymore and there have been occasions where I’ve cried straight afterwards, which really ruins the situation (thank you, brain). I feel this almost paralysing fear that he won’t want me if I don’t want sex, and I don’t know how to work through it. Sorry this has been quite detailed and a bit of a rant. I’d appreciate any advice or just to know I’m not the only one who’s experienced something like this. Thank you