My gf broke up with me because of these things I did with my ex? She is heavilty catholic?

Don't blame your stupidity on her religious beliefs. They had nothing to do with it.You don't even have to be religious at all to get mad over contact such as you had with your ex. You were wrong to do anything with an ex other than maybe saying "Hi" passing by her on a street. Exes aren't even good to make friends with, especially when there's already another girl in the picture.