First off we can all sit here and scold you for getting involved with a married man. But the fact of the matter is that you did and now you're in a less than desirable situation. There is no turning back and changing what has already occurred.
But you're heart and gut is telling you what to do and you should go with that. Because your gut is usually right. This man has proven himself to be unfaithful. You can not guarentee that he will be any different with you. You are young and worthy of a fulfilling relationship. So moving on may be painful but you know it's the right thing for you to do.
I'd suggest that you get yourself involved with other things to take your attention away from him. When you are not there and available to him, he may very well start the manipulation game and try to talk his way back into your life. You need to be strong and do what is right for you.
By standing up for yourself and getting past this you will feel so much better about yourself. You are a strong woman and you can do this.
I'll check back in to see how you're holding up. But protect your heart, save it for someone who will cherish you!