when these confusing situations arise i honestly believe confronting the other person always sets things straight. If you are interested in being with your ex and possible patching things up then ask him if thats what he wants as well. I was in a similar situation with my ex. I dated mine for four years on and off and the one prblem i encountered was that the same issues always arise. Theres a reason why you didnt work out the first time and you should make sure that this issue wont come up again.
Confront him tell him how you feel and what you want, his reaction will give you all your answers
as for the girlfriend she may be a distraction for him or maybe he is serious about her. Once again hell let you know


