Most Helpful Girl
You're not making a mistake.
No matter what, he was deceiving you. He was disrespecting you. He was disrespecting the other girl.
He may love you. Many here will tell you he's a cheater and he doesn't, but he may indeed love you. What is a fact is he does not respect you the way he should, and he either needs to learn how to do that or leave the relationship. He needs to find a way to earn back your trust. He has hurt you deeply, and he needs to make up for it.
How you go about this situation is your decision. I would advise you to essentially break up and see how he handles it, but this is your life. I don't have to deal with the consequences.1THIS IS NOT RELEVANT ANYMORE