It seems that he is going through a very selfish period as well as a crisis. Any way you take him back now he will still have the best of both worlds. If he is on a dating website he is moving on. That says I want to meet someone new. You are unfortunately wasting your time. If you continue to hold on to the idea that you are in a stable relationship than he will have his cake and eat it too. He is finished with the relationship but has all the benefits. I understand why you feel rejected. The best way to remedy that is to find closure and let this go. Develop ways to coparent and let him move on which he is doing anyway. You will continue to be hurt if you don't accept all the signs that he is giving you. Find someone who wants a monogamous relationship. You have to accept the obvious.
If this has been helpful press accept