I have a problem and I need help. I'm not a forever alone guy, in fact, I have a girlfriend at the moment but my problem is not that, the problem is that every time I hear one of my exes get a BF I get mad and find a way to fuck it up for them. I know I'm a piece of shit of a person and I have no excuse for doing this to 3 different girls but I can't help it, so I'm seeking help.

What do you think it's the root of this problem and how can I stop getting mad to girls I already dumped (besides the first one which when I fucked up her relationship with her boyfriend after me I validated myself saying it was because she dumped me but yet I'm doing it again)

Help?