Ex-fiance wants me back - dream come true?

We dated for 4 years. From day 1, he was insecure, jealous and not very nice to me. Still, I loved him though there was always tension between us, and I constantly wanted out of the relationship. We got engaged, but 3 months before the wedding, thinking he was too good for me, he called off the wedding and moved out. He went on our "honeymoon" without me, replaced me with another girl, and told me, brutally, that he loved his life without me and I am pathetic for begging him to reconsider throwing everything away. I fell into deep depression. Then, I met a handsome, simple, good man who has shown me nothing but respect and love and who I have grown to love very much in the past 5 months. However, the ex has returned, telling me all I prayed he would tell me: that he was awful, that he has changed, that he has had an epiphany and that he will treat me the way I should be treated if I only give him another chance. Do I throw away the 4 years or the chance of love with new guy?