Advice needed please

I have been in a relationship for 7 years. I have 2 sons aged 10 and 13 from a previous relationship. At first I thought he was the real thing, he said he couldn’t lie and would never cheat. At the start it seemed to be things like him liking Facebook profiles ( usually of women with hardly any clothes on), while it made me jealous , I accepted it, I had nagging doubts as we had met on a dating site that he was still on them so I logged on under a different name and there he was. With hindsight I should have ended the relationship then but he said he wouldn’t do it again. To cut a long story short I’ve had a rough few years losing a parent to cancer and suffering depression. I have throughout the years found him on dating sites upwards of 30 times. The last time I found out he was upto something was a search on his phone for dirty kik women and cam girls. I feel very sad that I have wasted the most precious years of my sons lives with him, I also feel bitter because my dad hated him and didn’t want me with him and he died without it being resolved. Now I’m in a situation where I have no confidence at all, the cheater is full of confidence. I keep thinking well it was a year ago since I found him upto something, maybe he’s changed?, I’m so mixed up. When I tried to end it a month ago, and he was looking for flats I was in an awful state, my anxiety was sky high at the thought of him going, which I can’t understand after all he’s done. Am I over reacting about the cam girls ?, also the day after my dad died , he went out to see his family, while my world had ended. I just don’t know what to do anymore, anyone who takes the time and effort to reply I thank you. I can’t understand why the logical part of my brain is saying get rid yet I can’t