How to get your ex forgive you for past mistakes?

Hello everybody, I’m new here and English is not my mother language, so forgive me if I make some spelling or grammar mistakes.

Everything begun last december when we met. For 5 months we had a really great relationship, with some up and downs, but generally we could connect very easily, we had fun and we were really well together.

We broke up about little more than one month ago. Although the relationship was good at beginning, there were some base problems I would like to point out. First, at the very beginning I were her rebound relationship, she told me after about 4 months, she decided to tell me by her initiative, so I appreciated her honesty and I’ve accepted, also because she said I weren’t a rebound anymore for her. I could tell she really liked me a lot, but maybe this may have contributed to the break up in some way.

Second and actually the most important, I found out I may have some attachment issue when it comes to girls I fall in love to. I don’t want to tell in detail here about all my psychological insights on this post, but if you search informations about excessive and anxious attachment you may get some idea about what I mean. I’m firmly convinced that this issue was the main cause for the break up as it made me become somebody I don’t like and that represents the very least part of myself.

Third, I’ve told you about how I were a rebound for her, I quite did a similar, if not worse, thing. I had another girlfriend before meeting her (For simplify let’s name the girl I’ve met in december ExA and the other ex girlfriend ExB). I had a three years relationship with ExB but I weren’t satisfied and I had hard time breaking up because she were treathening to commit suicide and I was truly scared to become responsible of someone’s death. Meanwhile I’ve met ExA and I really fell in love with her, so I inevitably cheated on ExB. If I would have kept the silence ExA and ExB wouldn’t have found out about this affair. But the more I were carrying on this lie the more the feeling of guilty became unbearable and I was morally forced to make a choice. I choosed ExA and I broke up with ExB. It was about two weeks before I also broke up with ExA.
The break up with ExB was horrible and really devasting for both of us, she stopped contacting me for a while and I could hardly sleep on the thought she might really have killed herself (which fortunately didn’t happen), meanwhile ExA passed for being ultra sweet and attracted to me to being extremly harsh due to me “not acting like a man and being weak”, that was caused by my attachment issue and the stress from the break up with ExB.

I couldn’t bear my guilt anymore and I decided to tell the truth about ExB to ExA. I’ve told her I’ve broke up with my Ex be 4 months after I met with ExA. She got mad and she didn’t let me the time to explain her all the issue. She walked away and never tried to contact me. I’ve just sent her one text the day she got mad, but as my head weren’t clear I were unable to explain everything to her. I’ve also sent a letter to her last week.

I know cheating is not a good thing and it’s not something I’ve would have done in a normal situation. My fear of having an ex who would kill herself made very difficult for me to act in a clear and consistent way. I can understand how ExA is feeling and she is right to be mad because I lied to her. She may think now that I am an asshole, while what I wanted to do is avoiding somebody to get hurt.

After a month she walked away, she erased my from facebook. Even though she didn’t block me and she may still be able to see my texts, she doesn’t seem to be easily reachable.
At the moment I don’t want to have her back as a girlfriend and I accepted that it may not happen anymore, I realised that I’m not ready for a committed relationship yet and I’m considering seeing a therapist for my attachment issue. But I would really like to solve all those misunderstanding and making peace with her. After all 5 month together with her still mean a lot for me and it is a pity to end up like that for.

Maybe I should just leave her time to make her bad feelings go away, I’m doing quite good by not texting her all the time. I just have hard time healing from all those problems and I think that just her forgiveness would really help me a lot.

I know the issue is quite complex and my English isn’t perfect, so if I left something unclear please tell me and I will try to reformulate.