How to forgive/when to stop forgiving

My partner and I are best friends. He is sweet and very kind to me most of the time. He's the type that will get up and go out to the grocery store in the middle of the night to grab me cookies or something else I'm craving. You would think our relationship is perfect from the outside, but there are some serious problems too. First, when we were just dating I found out that he hid a video camera in his bathroom to videotape my friend changing. I confronted him about this, he denied it and then later came clean. So not only did he do this, but he lied to me. I forgave him. He did it again a few years later to my mom. Again, I forgave him. Also in our early dating years we had a few threesomes. This was fun for a couple times, but once we got married I was ready to settle down and it just be us. But he kept pushing & pushing them and so eventually it started wearing on my self worth. After about a year of marriage he brought up wanting to go have sex with a girl who we did have a threesome with a few years before. At this time in our relationship I was so used to him pushing to get what he wanted, being self conscious and afraid to speak up that I didn't really say no. I know through my actions I made it clear I was upset with it, but he did it anyway. The next day after a serious breakdown/confessing to him that I was in so much pain I wanted to die, he apologized and said "maybe it had to get to this point for me to change." So, I forgave him. Our relationship was hanging together loosely for the next two years. One day I realized that I needed to let go of the past and that he was doing really well and I should move on and forget my old pain. It was hard because sex for me had become a painful thing because it was the root of all our marital problems. Anyways, for about a year things were a lot better. Then about 3 months ago we had a mutual friend ov er. She was a very flirty type and I could tell that if she came over and drank with us (which is what she suggested) that there was a chance she or my husband might try to make it more than just a friendly hang out. So I told him I didn't want us to drink, just to go out to lunch because I didn't want anything to happen. Long story short... he and her did drink. She did get super flirty and weird. She said when she got drunk she wanted her clothes off, so he took them off for her, she sat on his lap naked, etc. They didn't actually do anything sexual together but I was sitting there in shock! I wanted to leave the house right then and never come back, but I didn't want to make her feel awkward. I told him the next evening that I was leaving him. He apologized for what he did and this time, for once, genuinely seemed sorry. He said he didn't know why he did those things. And that he didn't think about it or my feelings when he did them. The next couple days were rocky, but eventually, as always, I forgave him. But since then things have felt like roommates. I realized a couple weeks ago that I just don't love him anymore. But we have so much fun together in other aspects of life... I just can't move on from what he's done. I told him this weekend that I am going to leave. And I am making sure I stick to it this time. I want things to get better, but I don't know if they can really. How many times can you forgive someone for the same thing? What would you do or recommend I do in this situation? I'm so lost and have no friends or family to talk to about it.

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