JUST FOUND OUT MY HUSBAND CHEATED ON ME!! Please help, thank you!?

[Pree_Girl]

First off let me start off by saying that this was not the first time, my husband and I met back in high school and got pregnant after high school. He cheated on me when I was 6 months pregnant. I forgave him and gave him a second chance after discussing that he admitted made a mistake and was very nervous being young and so many responsibilities.. ANYWAY... Now we are 27 yrs old and 3 daughters later he has done again, he cheated on me with a co-worker. This happened about a year ago but He just recently confessed after me attacking him with questions and left him no choice. He said he had a relationship with her and slept with her and went to vegas together.. The only reason I found out was because of instagram she blocked me on instagram and I thought that was weird because she didn't know me and why would you block a random stranger??... I had my other suspicions about it but never brought it up. He said he ended the relationship with her because he got tired of living a double life. he said she got very upset and threatened with calling me and telling me all the truth. This broke my heart and I told him I want the divorce but he cannot move because he has no where else to go also he has lost his Job so he only has me. He said he loves me and that it was a mistake and to give him another chance to prove to me that he is a changed man and that she meant nothing. I truly don't believe him and think that he will do it again if he has the chance. I don't know what to do because we have three daughters and a lot of years invested. We are happy when we are together and we get along pretty good. He is like my best friend and I love him. I know if I left him I would not have a problem finding someone better. But at the end all men are the same... She is a very gorgeous and beautiful girl and SOMETIMES I feel like sending a message to the girl letting her know he is available and she can keep him and take him back because I don't want him ANYMORE!!, Pelase Help I don't know what to do and I am scared of going out into the real world since I have never been with anyone else but him.