Sorry you're struggling with this. I don't think anyone can really say what exactly the problem is. But it really sounds like a big part of this problem is anxiety about it, a phobic reaction and disgust at it. What I was reading into it, was that perhaps you have a fear of intimacy (not exactly sex, but the intimacy it entails) and that's why you're having such a strong phobic response to it. Just a lot of what you described, sounds more like a phobia and intimacy fears and discomfort, versus just asexuality which is usually just a general disinterest in sex (which can involve repulsion, so I'm not saying you don't have it), and you said you still have an interest in sexual things, which an asexual wouldn't.
Do you have a therapist? I think it would really help to talk to a professional about this and find out what the problem is. And if the problem is a fear of intimacy, then perhaps they can help you overcome it.