The Biggiest Drama of my life because of him

I have been married for 3 years now and my husband and I started to work after a year at a hotel part time to make extra money. We met two girls from Ukraine and became friends with them. I could tell there was some kind of Chemistry between one of the girls and my husband, so I broke off the friendship with the girls because of it. My husband has been acting strange now for a year and a half after the time we left the hotel and I stopped that friendship. I had to be my own investigator and find out that my husband had signs of cheating. One night a couple months ago he didn't come home when he said he would, so I jumped in a car and went to where I know he usually likes to hang out and sure enough caught him red handed driving beside me in a car with a girl. Two weeks after I still found more that there was someone else too many weird numbers on his cell phone. Sure enough I caught him again and asked if he had sex with this one and he said yes. He created a story to cover the truth that hurt like hell. Sure enough it turned out to be one of the girls that I ended the friendship with and he had been with her intamitly for a year and a half every chance he got. He also slept with the other girl the one time. He lied to me and made me belive our problems were only ours. He had no reason to do it and knows it was wrong, but has no idea how devistated I am. I knew this girl and the room mate he slept with once. The girl in the car he almost did it with, but didn't. He is a manipulative freak who took advantage of my love for him and doesn't realize what he will loose if I leave him. I want to leave, but now he is saying that he would never do it again and that it made him appreciate me. I found out all the dirty details and it hurts even more. The part that hurts the most is I trusted him and at one time this girl was my friend. I don't know what to do. If he was just my boyfriend I would be running for the hills, but this would be divorce. It's just going to take one thing and I am out. I can't forgive him, because it was an affair not a once thing. And he slept with the other girl/friend/room mate! Then the girl in the car. I am sorry, but I think 3 strikes and your out! I am a real looser for staying with him and he makes me very weak. Is it worth it? Once a cheater always a cheater right? Is he genuine or is he just going to be more careful next time. I need HELP!