If this initial relationship that you described had nearly as profound of an impact on your life as you believe is possible then a possible explanation to your current behavioral problems could play out as this:
You trusted her, did everything you thought was right and gave all the good that you had in you to give. She betrayed that trust and so two possible assumptions were made. The first assumption was the idea that perhaps more women are just as manipulative and as mean as her, and if so... maybe they are the majority. The second being that you let your guard down and felt that maybe you deserved getting hurt for it. So in this possible scenario... you do not respect women at all, because you feel resentment towards the one that initially hurt you, and then seeing the willingness of these later women to cheat with you, only seemed to confirm your original suspicions. And you do not feel that you deserve to get hurt again, so you never let them too close... you never let them into your heart, not really.
If this were to be the case, then it's a matter of regaining your trust in women. You will have to take the time to realize on a subconscious level that not all women are bad... and quite a few have just as many scars, if not more than you from their dealings with lovers that were never fair or true. Essentially that we all get hurt, we have to pick ourselves up, try again, and try very hard to not pull the assumptions from the last relationship and have it taint the new relationship.
It is my personal opinion that your cheating is a defense mechanism put in place by you (whether you realize it or not) to safeguard your heart from the pain and humiliation that you had once or repeatedly felt. Some men are naturally inclined to cheat, whereas others... like you, possibly... use it like a shield.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen