Not Sure What To Do About Husband

I have been married for 14 years and over than time we have had relationship problems just like every other couple.  About two months ago my husband said that he wanted to be sinlge.  I was shocked and heart-broken!  We have four children and I quit my job last fall to spend more time with my children because my husband was driving truck all over the country.  I feared being left with four kids and no income.  I almost feel like I begged him to stay because I was so afraid to be alone. Since the initial shock of our conversation we had decided to work things out for the sake of our children. Not sure if that was smart or not.  Here comes the even worse part, I was snooping through his wallet one day and came across a piece of paper that was filled with on-line sex dating site along with all his user names and passwords.  Late one night, I visited these sites.  I noted dates that he had signed up for these sites as well as any contact he had with other people.  After I became sickened by the information I would I confronted him.  He lied about the whole thing!  Eventually he told me the truth about everything.  He admitted visiting the sites over the previous 16 months.  He even signed up for a new site within one week of when I quit my job.  I was devistated.  I really questioned if I should have stayed with him or not.  I am so confused.  I don't blame myself for this situation.  Regardless if I was crabby or not sexually interested every moment of the day, that didn't give him the rite to do this.  I wonder if I am so afraid to be alone that I am staying with a cheater.  He says he never cheated.  I even went so far as to make copies of every web-site he was on and his contact list.  I contacted some of the people on the list hoping that one of them would tell me that they had been with him.  What do I do???