I cheated with a married woman.
Why did you feel that you needed to cheat?
Because I hated my life and didn't care about what would happen. Also I'm married to my girlfriend.
I think that you need to come clean about what happened. It is wrong to have relations with someone if you are both married.
I don't give a shit about cheating.
I do not think you would like it if your girlfriend were to cheat on you. You should  have extended that same courtesy to your girlfriend and not cheated on her. Come clean to her.