This is a good question. I've experienced this before, I'm sure other people have too. Its infuriating. Correct me if I'm wrong, but it sounds like when you're having sex, you don't feel totally emotionally connected, and that spikes her anxiety and makes you question things in a ruminatory way? I think if you're scared that you don't love your boyfriend, it probably means that you really love your boyfriend and you really want your relationship to work, but you're feeling detached possibly. Do you guys typically just jump right into sex? Like does he get in the mood, start laying down some moves on you, and then you just slide right into it? That can be fine, for many people it is, but what I found is that doesn't work for me either. It feels like a chore. Maybe what you need is to work with your boyfriend to cultivate desire throughout the day. Maybe what makes you feel intimate and connected with him and a desire to express that through sex, is nonsexual intimacy in the hours leading up to sex. A lot of men subconsciously use sex as a way to connect and feel intimate, and thats fine, but for many women in relationships sex can often be the EXPRESSION of the love, intimacy, and connectedness they feel with their partner in all the non-sexual areas of their day. The most effective "foreplay" in this case is laughter, joy, playful flirting, feeling protected, respected, and supported, seeing him do things that make you feel just so much respext, admiration, and love for the content of his character that you just wanna express that through sex
Its possible you dont love him. But its also possible that youre going through a SUPER normal period in ur relationship where you arent connecting much outside of sex. It takes a LOT of work, but thats what a relationship is about. "Love" isnt just a permanent guaranteed emotion, its the byproduct of you both GRINDING to cultivate the safety, desire, trust, and connection every day necessary for that feeling to survive.