Welcome to the forum. I'd like to advise you to stop calling yourself names. That's not getting you anywhere. It sounds to me as though you are doing more thinking than living. It also seems as if you are trying to convince yourself that you're straight. Posting your musings on a gay website ought to tell you something.
What do you think your issue is with not finding genitals attractive and jerking off to shirtless men? Are you afraid of intimacy? Are you sexually insecure or do you have performance anxiety. While there are certain expectations with male/female sexual relationships, gay guys can opt to define their sex play more freely. What you do or don't do would be up to you and your partner.
You don't mention friends. If you're not relating to people in social situations outside of the classroom I'd suggest that's where you ought to start. Join a study group or a club. In any case I think it would be best if you thought less and acted more. If you're going to limit life to figuring things out you'll cheat yourself out of experiences which will lead you to the truth. If you have serious issues relating to people I'd suggest some therapy to help you with that.
You might want to send some PMs to people here with whom your comfortable. In any case, I hope you become an active member and keep posting.
I'm really glad you're here attempting to make some sense of things at 20 rather than 40. Good luck to you.