Your Chances Are Slim
Before making any moves, I think you need to determine honestly if there is any chance of a future for the two of you.
Since he is in a different state and has a girlfriend, it looks as though the chances are slim, at least for now.
Time To Walk Away From The Relationship
So what would you accomplish by staying in touch with him? Your relationship would probably not get any closer, since he is obviously focusing his attention on his girlfriend. This would be frustrating for you.
Even if he did keep in touch with you, hearing about his new girlfriend wouldn't be a picnic either. The more you correspond with him, the more your feelings may intensify, which will make it worse in the long run to walk away from the relationship.
This may be very difficult to do, but I would give him some space right now and simply wait to see if he contacts you.
Don't Call Him, Let Him Call You
People often say things like "we should stay in touch" or "let's get together sometime." That is easy to say, but not always truthful. If he really means it and wants to stay in touch with you, he will do it because it will be important to him.
We live out our priorities!!!
Since you know he has your number, he will call you if his feelings ever change toward you and pursuing a relationship with you is really what he wants. So, I would not call but just leave the ball in his court.