What troubles me is this - "he cheated on me for the first 6 months of our relationship" (did you get a reason?) "I found out" (did he tell you or did you discover based on evidence found?), "nor is he going to have the conversation every few months or weeks whenever I have a breakdown" "he doesn't seem to have much remorse for the damage he caused" (a biggie for me possibly deal breaker), "He has told me several times that I need to let it go or move on". He said he would do anything to make it all better for you but when you need to discuss your fears he drops the gavel and says "NO TALKING ABOUT IT - SUBJECT IS OFF LIMITS!". How convenient for him to make up all the rules and expect you to obey them or "move on". He must feel he has some power over you (sounds like you've given him that too).

Why would you think that you are the cause of his cheating? Is there any basis to that? Not looking for a response to any questions, just postulating. No one knows all the facets of your relationship. Just be careful, whatever you do. Sorry you are dealing with this.