How to stop this downward spiral?

I had a unpleasant childhood. My dad died when i was 3. I was totally controlled and frequently abused during my gradeschool years by my stepdad. I got into some trouble in middle school. I failed the 11th grade. I got my first wife pregnant when we were both16 and dropped out of college. I managged to get my ged and got 2 years of college done by the time i was 20 while helping to take care of my baby son and working. My first wife and i got married when i was 20 and she got pregnant again and i joined the army. She cheqted on me. And stayed out all night every night, so i left her. She abaandoned the kids, so i took them for 6 months. She got into trouble and nearly went to jail, but i bailed her out. I took her back. Then she got pregnant again. A year later i got out of the army. But rather than continuing to work, she went out all day and stayed out every night, so i left her. But she tried to committ suicide and got on drugs, so after a month i got the kids. After 6 years of being on drugs and mostly being lost without a trace and me being the single dad of 3 kids she got clean and stable, so we tried to reconcile aagain. By then id had a few failed relationships which seemed to fall apart because of the kids. By then i also had a decent job, but my job was 2 hours away from my mom's house where i had been living. We got our own place, but after a year my mom and my first wife talked me into buying a house to share. 2 yrars later the house was $75000 under water, and my first wife left me for an 18-year old (half her age at this point), and took my kids. I fought but she got full custody and i get to see my kids once a week for about 8 hours, provided they're not too busy. I also lost 20K in the divorce. I remarried a new woman right away, being stupid, and she cheated on me and left me 6 month later. For the last 6 years ive been commuting 5 hours a day too. I pay half my paycheck in child support and only have 700 after unavoidable bills.