Dear Happi:

My answer is that there is no easy solution to your problem. If you stay with him, you suffer. If you break up with him, you suffer.

Your choice is between two experiences of suffering.

You are too willing to accept everything he says in your aim at avoiding the second suffering, the one to follow breaking up with him.

He told you that he will do whatever for you, for the relationship and then he will not stop talking to her. So he is not doing whatever. 

Choose the kind of suffering where you do see reality for what it is. Reject the suffering that involves you being very confused. Choose clarity over confusion. From personal experience, the suffering involved in being confused is more excruciating, far more excruciating than that involves the process of opening the eyes and ears to reality.

anita