Mistake, decision, choice, whatever you want to call it, he acknowledged that his behavior was wrong. I'm not condoning it but I think we can dispense hard truths and tough love without name-calling, viciousness, and cruelty. The way you're acting, I could mistake you for the one that's been cheated on.
@RRokh I think part of the reason your post has touched such a nerve with some of us is that many of the spectrum, myself included, struggle to form
any romantic attachments. As I mentioned, I've only recently had my first significant relationship and I'm 34. That's despite actively seeking one from a very young age.
It seems that you have been lucky enough to have romantic relationships but have for some reason sabotaged them with infidelity and lies. You have something that many of us desire but once you have it, don't seem to treat it like you value it. I also suspect that many of us have felt victimized or mistreated by others at various points in our lives, as such, it's easy to identify with your girlfriend and the pain she must be experiencing.
That said, I think it's unfortunate that some of us feel the need to attack, make fun, name call, and attempt to drag you through the mud. None of us know you personally and therefore our opinions regarding your character, conditions, etc., are based on very limited information. So I hope you take them with a grain of salt.
I agree with you and others that the way you treated your relationship and your girlfriend was shameful, destructive, and extremely problematic. However, it seems that you are trying to understand yourself, your actions, and what role, if any, your autism had in this situation. I commend you for that. Whether or not your relationship can be saved is ultimately up to your girlfriend but I hope this forum and other resources can help with your introspection.