Piece of advice my friend. Everybody deserves a second chance but it your gf cheated on you many times I think you have to think twice my friend because if she really loves you she will never cheat and she will never do things that will hurt you or ruin your relationship. I know u love her but please love yourself too. Self love is never selfish. Don't beg someone to stay on your life , you are more than that true love is given freely. Once the trust is broken it cannot be fixed easily. Someday, someone will come in your way and will love u and treat you right.