Obviously he did not have your interest in mind when he decided to forsake his commitment to you in favor of another warm body. Hopefully you and he have gotten an AIDS test before jumping in the sack again. Of course, you can't always be too sure if he's bringing you any additional presents such as herpes, gonorrhea, syphilis or another sexually transmitted disease. Fool me twice, shame on me. You are very young, and in my most humble opinion, would be very foolish to continue to let him play with your heart.
Marriage is the eye-opener.
Your eyes are now wide open. Take off the blindfold. He has lied and cheated on you at least twice. Each time he comes back to you with his tail between his legs only after he has been caught in a lie, and tries to fill your head with words that he knows you want to hear. I have women coming to see me after marriage with the same story.