So, here's the thing:
Can you change what happened with your girlfriend and her ex-boyfriend?
Can she travel back in time and not have sex with him?
Is there anything at all you or her can do to change the fact that she had sex with this other guy?
Unless, you have super powers, I'm guessing the answer is most definite
NO
So, the real problem isn't that she has already had sex with someone else or that her ex-boyfriend is a jerk. The problem lies within you and it's something that you'll need to fix yourself.
Usually, when guys have feelings of jealousy it's because they are not confident in themselves.
So how do you fix it? That's a tough question and will likely involve much personal introspection. The easy answer is to simply "not give a sh*t" about external forces and focus on you!
Hope that helps
