I (21 F) find sex disgusting with my boyfriend (28 M). Help.

Before you think I‘m asexual, no. I love sex. But weirdly enough as soon as I hit a 7 or 8 month mark in a relationship, I start to find my partner repulsive. Does that make sense? In my current relationship, my boyfriend doesn’t like any foreplay, he just slides right in and calls it a day after 5 seconds, unfortunately I‘m not joking and I know I’m not the only woman experiencing this. We have had great experiences in the past, that is why I haven’t given up yet, unfortunately they are very rare and ultimately I’m disappointed and dissatisfied most of the time after a session. My partner is starting to suspect that I am cheating because I don’t want to have sex with him. We have been together for almost 9 months now and we haven’t slept together for 3 weeks now or something like that. The thing is I also experienced this in my first relationship where we had no problems in bed whatsoever, he was a sex goddess. But his personality sucked. Now in my current relationship, it’s the other way around I fear.

I am seriously considering breaking up with him over this. Before you come at me, please validate my feelings for a second.