Bi girl in a het relationship - Advice for Sexual Insecurity/Relationship Rut?

I don't want to have sex with my boyfriend anymore. We've been together for over a year now. I realize that this is unhealthy, but I can honestly say that I never really enjoyed having penetrative sex in the first place. Oral sex between us has been good. We used to have sex fairly often although I was usually doing it for his sake, either as a romantic gesture or because I would've felt bad saying no. He's also a very sweaty dude and I used to look past it but lately the sweatiness has been a real turnoff. He has to sleep with a fan on him every night or he will literally soak the sheets with sweat.

He keeps saying that he doesn't feel close to me sexually and he wants to know what's up but I never give him a straight answer because even I, myself, have no idea what is wrong with me. The thought of having sex with him makes me nervous and uncomfortable, and I'm relieved when I think "the coast is clear". I still watch porn by myself but the thought of being intimate with him makes me uneasy. I've had sex with about 10 guys before but never achieved orgasm with a male/actually enjoyed sex until my current boyfriend, and even then I was willing myself to do so by thinking about women. I think it all has to do with my attitude toward sex and personal insecurities, though.

I'm not gay, I'm bisexual, and I KNOW for a fact that I am attracted to men. Also, I may be in a heterosexual relationship but that does not make me any less gay (in the bisexual sense), so please don't judge. Gosh bisexuality is really complicated, I feel like I have to defend myself from everyone.

Anyway, I'm worried that I actually enjoy denying my boyfriend somehow. Like, I take pleasure in turning him down. That sure doesn't sound healthy at all, especially since we signed a lease several months ago for an apartment and we are about to move in. Oy vey. Does anyone have advice for overcoming sexual insecurities or relationship ruts?