I feel I'm stuck in the past?

I was in happy relationship then problem after problem did lead to break up I accepted that and moved on in fact my ex did hurt me deeply and I had to just leave the situation.
Anyway my mom had cancer and she passed away I couldn't handle the pain I felt I was going to get heart attack I contacted my ex I told her please just stay with me I can't handle that much of pain she said never mind I'm here for you anytime for a week everything was fine and then I started to bring up the past and why she did this and that at this point she Said I'm here only because you asked me to stay there's nothing more to talk about. I don't really know at that point I Lost mind and I blocked her she got very upset. Later apologized to her but she was holding everything. Anyway she said I want nothing to do with you and we are totally done. I accepted that too but I sometimes get flashback about that relationship it wasn't normal I had 8 relationship none of them were like that she was there when my mom got Cancer and she was there in my worst Time and worst chapter of my life that's one of the reasons I can't delete her completely. I'm not sure what to do even when I talk with new girls I feel I'm cheating my ex. What should I do? I'm damn stuck
I feel I'm stuck in the past?
Post Opinion