Is he a true cheater?

So I met this wonderful guy. He's a total sweetheart and he knows how to treat a girl. He left to a foreign country for a month while we were talking (not dating) and he slept with another girl while he was there. When he came back, he acted as if things were just like they had left off. Then I found out and he apologized and I forgave him. Then one of my girl friends told me he was trying to get with one of her friends. I didn't believe her but I still had that feeling in my gut that told me he was. Today i went snooping thru his face book (I know...if I look for trouble, I'm gunna find it) and I saw him messaging a girl saying how "f**ing hot she was". I don't want to waste my time. I'd talk to him about it but I'm really gullible and he's very convincing. What should I do? [Im on an island where the ratio of females:males is 1:20 so moving on wouldnt be hard...I just want to see an outsiders opinion]