Is it normal I had sex with my cousins girlfriend?

I completely agree with this. You are a horrible person for what you have done. This is your family and you would do this to him. Who cares if he found out or not. You should not have been doing it period. Did you ever once think about how your cousin felt? His girlfriend is an unfaithful cheating bitch. He probobly broke up for her for similar reasons even if he did not realize she was cheating. You were fourteen but you still had a choice of where to stick your dick you little prick. I hope you get an STD.