I love my boyfriend but lately I don’t know if I’m happy

We have been together for about 1 1/2 years and it’s been a constant roller coaster. I fell hard for him and I believe he did for me but so much of what happened in the past, I think is still effecting me. I found out he cheated with his ex right after we moved in together and she was almost stalking me she found me on all social media’s, would send me friend requests after I deny her several times, had her friends add me on Snapchat and they were constantly watching what I posted( which I had my sc public) and I always had ppl who I didn’t know on there so I never thought anything on it. She told me she got pregnant by him but had an abortion but I still am not 100 percent if that’s true. She asked him for money and he asked her to send him some paperwork or anything confirming to pregnancy or procedure and she never did. 🤷🏾‍♀️ Besides all that I knew making the decision to take him back and work on this relationship met that I couldn’t hold on to the past to move forward so that’s what I’ve been attempting to do for the past several months. I’ve made the decision to try to work on this because we have great chemistry, love, we get along great for the most part, but I don’t know if I’m too broken to completely get over the past. This weekend is his birthday and he has been talking about it for weeks that he just wants to have a good time with me and enjoy the weekend but I’m not in a mood to really celebrate anything with him so I’m just wondering if I should continue to work on this? When do you finally know it’s time to end a relationship?