Don't bother with him. You haven't spent a lot of time dating him so there is less invested in the relationship. Don't waste your time trying to keep a relationship with a guy who has shown TWICE that he is unable to commit.

You will be hurt less if you break it off now. It will hurt more if you spend years with him and he continues to do the same behavior. (Maybe he will be even more sneaky about it, which will hurt even more if you think he's been faithful for an extended amount of time....etc) There is more to life than heartache. You deserve to be happy, and to be in a loving relationship.