Thanks a lot for your reply, it's oddly comforting to know I'm not the only one, even if it is a not so good situation.
I'm definitely the same though, I guess I lucked out in the way that my girlfriend has only ever shared a tiny kiss with another guy when she was super young, otherwise she hasn't done anything. So it's like instead of focusing on what she's done with guys in the past, it's more so like I'm just freaking out over really stupid things with her male friends. And like you said, the guy I have in mind, I hate him with a purple passion, but rationally, like, I know it's so so stupid and I want desperately to get over it, there's really no good reason for me to dislike him.
I am pre-T, I hope to start by next year at the latest. I have a gut feeling that when I'm on T, my jealousy issues will die down to a great extent but I just wanted to get somebody else's advice because I hate to think of T as some miracle cure-all (although it's hard not to see it that way for a lot of my own issues). I did recently start working out consistently and it really does do wonders for my self esteem. I've been applying for jobs as well and if I get one and can afford new clothes I know that will help, and then from there it's off to therapy and hopefully hormones.
Thank you again for your reply, you have no idea how much it puts my mind at ease. I hope things go better with your self esteem and jealousy as well, just remember like you said, it's self destructive behavior and we're always our own worst critics.