I’ve been on the other side of this so I may be able to give you a bit of his perspective.
I was in a relationship where my DP’s Ex had an affair and left him for another man, several years before I met him and since their divorce he had dated a few women before me.
I thought (naively) that because it had been quite a few years since they split and he’d had a few relationships in between that he was over their divorce and ready to commit.
But he (like you) hadn’t dealt with the demons and trauma that came from the breakdown of his marriage and his ExW’s infidelity.
The insecurities it created in him caused so many problems in our relationship and I felt like I was being blamed or punished for the way she had treated him, because literally none of this was my fault or anything to do with me.
He would over analyse messages, or if I didn’t text back straight away due to being busy then he would accuse me of ignoring him, or being cold towards him.
He needed constant reassurance and it was incredibly draining.
I would go to see him, excited to spend the evening together and he would blow hot and cold. I would never know what version of him I would get.
I’d arrive happy and full of love for him but he would at times brush me away, not let me touch him or cuddle him and be snappy in his responses to my attempts at making conversation.
It began to damage my self esteem. I felt like I was walking on egg shells at times and it became very suffocating.
My friends viewed it as controlling and mildly abusive. He was a good guy and I loved him immensely but I couldn’t take the constant love then coldness pattern.
OP... I think this is what you’re doing to him. It sounds so familiar.
You may have lost him, he may be more patient than I was and stick around a bit longer.
But to be blunt, if you don’t get counselling and sort out your problems you will definitely lose him in the long term.
If he has decided to call it quits, please don’t chase him or bombard him with texts or calls.
He’ll be hurting too and confused as to why you have been treating him this way. He can’t read your thoughts.