I almost cheated on my girlfriend
Do you want to tell me the reason why you almost cheated on your girlfriend?
No. I don't wanna discuss my love life with you.
I understand if you don't want to talk about it, but you still have to answer to your conscious and figure out why you were almost unfaithful.  If you don't ask yourself why you almost cheated, it's going to happen again and you could lose your girlfriends trust.
I'm never going to cheat on her. What I did wasn't that bad.
It's good that you're not planning to cheat on her, but the fact that you almost cheated on her should be addressed. If you face that sort of temptation again, you may give in and ruin your relationship in the process. You should talk to someone to help keep you honest in the future.