I have only been able to catch up a bit with your thread, but I find your comment about learning to be more "selfish" very interesting.
As an outsider looking in, I did get the impression that you were doing everything you could to please ex so that he would stay with you. it seems like you might have put your own beliefs and boundaries on the back shelf so that he would "like" you and stay in the relationship with you.
What is it that you seek in a relationship and partner? Did your ex actually fit what you wanted in a person? Did your relationship (I saw that it was open) meet your needs? You have the right to a partner who is committed only to you both physically and emotionally. Did you feel valued in your relationship?
I think that using this time to evaluate your needs and to make sure that you know how to assert your needs is very insightful and will help you to negotiate a healthy future relationship.
