I will just try and answer one question at once as it's a bit overwhelming.
Why did I do it?
I'm unsure fully but these are the things I know.
I felt quite unworthy of being loved by my partner because he's so great so I felt a bit fatalistic because I assumed he'd not love me anyway
I found it very hard to picture a happy future because it's not my experience that things are happy
I haven't got a template inside for healthy relationships as the world has always been scary (I've never cheated before) so I think before this I kept a certain distance
I have many personal flaws and poor coping mechanisms designed for self defence that I've been working on
Myself and partner were long distance for a year and I was thrown together with someone else (I firmly believe there's no way I would have done it if this wasn't the case)
That person I cheated with (I see now but didn't see then) was an abuser, and I was susceptible to love bombing because I had low self esteem
I will sound like I'm lying but I didn't want to cheat and wasn't infatuated with the man, it was just a calamity of factors. These aren't excuses I'm trying to just be honest.
There was never a minute I didn't love and want my partner, which sounds again like a lie but it's the truth. I know I made bad choices and wish I could rewind but I can't.
I am fairly sure I also have PTSD from the cheating itself. Not just my own actions to harm someone this much (the person I love most) but also because the man I cheated with was an abuser.
He was very nice / couldn't be nicer at first and that feeling of being "loved" or cared for appealed to this needy part of me. That quite quickly gave way to a cycle of abuse.
I ended the affair quickly (weeks) but the abuse continued (stalking, threats, some violence) and because I had cheated I as the bad person and didn't tell anybody. I thought at the time I deserved it.
So when my partner first found out about it all, I was initially so relieved to be able to tell someone, but it was the most guilt and shame and regret I've ever experienced. He was devastated but had a lot of empathy too so it was a lot of crying but gentle communication.
I was able to work really well at first with everything and my partner wasn't angry, but I think I fell by the wayside and things went off track.
I started experiencing full throttle PTSD about two months later, with feelings of irritation night terrors, severe depression and at that point made it "all about me".
My partner was patient but as people have said, eventually got resentful because his feelings were being pushed aside, so he started getting angry at me. He said the selfishness of cheating was mirrored in the selfishness of recovery.
He said he understands I have PTSD but it doesn't mean he can sweep my cheating under the rug and that I have to get help for myself so I can do the necessary work and learn to allow him to process what he's feeling.
I was just hoping there's some practical method that I can let him do that without rocketing anxiety because I honestly want to be able to do what he needs.
I'm not getting any help, but I've come close to emailing a few therapists. I really don't want to split up. I really love him and just can't cope at all with that idea.