Cheating is always a tough situation, but as Dr. Phil says, it's a dealbreaker. In my experience, the saying holds true, "once a cheater, always a cheater", but then there are always going to be those some men it doesn't pertain to. I don't know your BF, so who am I to say anything, but why do I not trust that he will seek help? Do you think that seeking help will get him to not cheat again? He betrayed you, and you may love him, but he needs to work hard to try to keep you in his life. See, men tend to take advantage of how loving women are and usually willing women are to forgive them. If he assumes that you'll always take him back, the less of a threat cheating on you is to him. I remember my ex-boyfriend told me on more than one occasion "Whatever, you know you'll always get back with me." and let me tell you, I changed my attitude real quick.
You have every right to be mad at him. Who goes out and cheats over an ARGUMENT?! That's not adult at all, and if that's all it takes is an argument and you rightfully getting mad because he wasn't being responsible, really, what does that say about him?
I know you don't want to leave him.
I would really hope he feels bad about what he did, but you have to make him prove it.
If he thought the relationship was really worth it, you better bet your @$$ that he'll do whatever it takes to keep it.
That's all I really have to say. I know it's tough though. Been here before

Good luck, hun!