He walked out when i was 7mnths preggo and moved in with another woman..........?

He has been sending me letters and sayin he wants me back! I got a letter today sayin he loves me blah blah blah but he completely ignored me when he was out of jail and he just walked out while i was preggo to be with another woman. He moved in with her left his clothes and everything! He has no job, car, house, clothes or anything hes never had anything! He has two other kids that he doesnt take care of and he was strung out on pcp. This is my first child and his 3rd child. I found the woman he was with on facebook the woman has two kids (not his) and shes not better lookn no car and no job! WTF! And he has cheated on me b4 with a 17year old and at the time he was 24. I no i wrote this before but i just want more advice. we been on and off for 6years now we have a two month old together that he denied when he ran off with the other woman! Now he wants to claim him. Hes in jail he gets out in december and wants to be a family! Does anyone think he was just using me the whole time and really wanted the other