I cheated on my gf with him and now I want more
Why did you cheat on your gf with him?
Because he's so much better than my girlfriend, and I want more
You shouldn't cheat on your gf with someone else. If you're not happy with your gf then you should break up with her.
I am going to stay with him. We do stuff together.
I can understand your new fascination with this person, but it is not fair to your current girlfriend. It is wrong to cheat so you should explain to your girlfriend what is going on.