I am going to jump right into competing commitments, here.
I'm wording this as though it is correct, understand that I realize this could be incorrect and feel free to correct me on any points.
For some reason, you "settled" for X1, knowing you were still pining for school sweetheart. You led X1 on to believe that you loved her and were committed to her, yet you concede you were lying to her. That, I think, is said in hind sight. I think that you were lying to yourself. That at some point in time, you convinced yourself that you were truly committed to X1 and loved her enough to M her and spend the rest of your life with her. Forgoing any future relationship with anyone, including childhood sweetheart.
What likely happened is very common and human, you ran into a wall of competing commitments. Your commitment to your own self interest rather than your M. Thus... your disengagement from X1 and ultimately X2.
No matter how much you indicate you loved X2 and how she was your soul mate, you once again reverted to being more committed to your own self interest than your X2.
I do not think you have a problem with commitment. I think you are really, really good at commitment. I think you are showing that in how you are taking on your life, gaining weight, making yourself better, meeting new people, etc. All things that are very self focused. And good for you...
Where's your balance?
It is OK if you will seek self preservation over the interests of others. Again, that's human. When we hit an abyss with the only choice appearing to be helping ourselves while others suffer or helping others while we suffer, many humans choose the former.
My challenge to you, is...
How can you be MORE committed to another over your own self interest?
