Why do women keep leaving me for jerks?

I do not have a great track record with women and I don't know why. There are three time in my life when I have lost serious relationships (one was a marriage) to men that were, for lack of a better term, jerks. I have been told I am a real nice guy that has a lot to offer. I work hard, have my own home, raised my sons on my own, have a good secure job and have been told I am good looking. I treat my women well, with kindness, patience and I have a very romantic side to me. This past week I lost a wonderful woman that decided to go back to her last relationship. The guy is verbally and emotionally abusive, he cheats and he doesn't offer any sort of kindness/romance (this is all according to her). But after a misunderstanding between us she decided to run back to him telling me that she never loved a man as much as she loved him. I'm now emotionally spent wondering why this has happened to me for the third time in my life. I'm sure there are some out there that have had similar experiences or who have some insight in to this phenomenon that I don't get. Please help me understand this. And not wise guys please. I'm just trying to get some understanding so I can find some peace.