What to do with a liar?

I have been with my boyfriend for almost three years. In the beggining I found out he was cheating with another girl for 3 months straight while seeing me at the same time, basically leading a double life. I broke it off, until about two weeks later he convinved me he was sorry and wanted to be with me. I took him back. About a year later a girl accuses my boyfriend of being the father of her unborn child. Turns out he slept with another girl during the two weeks we split. With a DNA test it turns out to be his baby. This was very devastating to me. But I decided since we were broken off I we could get through this together. As time goes by, I find out he was talking to one of his exes behind my back. They only spoke about 3-4 times in about a year, but my goodness if theres nothing going on any feelings towards this person why are you lieing and hiding it from me. And again I forgave him. Not to mention another incident where he gave his number to some random girl at a bar, b/c we argued. But here comes the latest incident. As my suspicions of him grew stronger, I became a detective. I checked out his phone call records online which he had no clue I could do. And I started investigating some phone numbers. There was a number in particular that caught my eye, which he was calling quite often. The times he would call was right when I would walk out the door to work. Eventually I found out it was a girl he was talking to on the phone for the past 3-4 months, once again I’m devastated and felt a blow to my stomach. I love this man so much and have put my all into my relationship and have done so much for him. How could he? Then, to add salt to the wound I find out the girl is an aquantance of mine, my neighbor. Oh boy, did my blood boil. I was furious, angry, upset. I felt the worse betrayal ever!! They both are pleading nothing happened between them.. But how can I forgive or forget such a thing. He always talked about how I shouldn’t associate myself with the neighbors but here he is having a secret relationship with one of them. I use to wave hello to this girl everymorning, even though I never even liked her. Our kids went to the same daycare, we even have mututal friends. How could they do this to me. I definately didn’t diserve this. So now, I ended any and all ties with my neigbor. And kicked my boyfriend to the curb. Now, he is begging and pleading, crying and sobbing for me to forgive him. He says he’s an idiot for what he did and I never disserved what he did. My son is all he knows as a father figure. I love him, but I don’t think I will ever be the same, I was traumatized over this. It’s only been a week since I found all this out. Please help me, should I give him anymore chances? There are more stories I could add of things he has done to lose my trust and push my heart away, but I think I’d be writing a book. What should I do, he keeps calling. We spent a couple nights together since then. The first night, I felt so happy to be around him. Then after a while I start hating him, I feel discusted just looking at him. I am just so confused. I think it’s obvious I should stay away. But I do care about him as a person.