Ok so my ex and I were together off and on for 6 months. The first time we broke up he kind of kept an eye on me and after some time we became close again and gave us another shot. The second time out was a huge fight between us until one of our friends told us to both pull out heads out of our asses and talk to each other and from there we got back together again and then he cheated.

After that I went on the war path until one of my friends took me to my old church a few months later and I talked to my old pastor about it and he suggested that I reach out to him as a friend to get some friendly closure because we were best friends before any of this started. So I messaged him asking how he's been and it was really awkward at first and he told me that what happened was an accident and that's difficult to explain. I told him I wasn't interested in an explanation. What was the point really? What's done is done.

After that it got a little less awkward and we started kind of poking fun at each other again which is where alarms started going off in my head. This is pretty much how everything started each time. We talk for a few days and then he's flirting hardcore and then he asks for another chance with the most sincere expression on his face.

What I don't know is WHY he keeps asking for another chance every time we start to get comfortable as friends again

Some couples struggle to go back to being friends when they've been in a relationship.
He might be getting mixed signals off you, seeing as you don't seem mad at him anymore & you two have got back into that playful routine of poking fun at each other, he might see it as his chance to give things another go.
You need closure and he doesn't seem over your relationship. It might be best to give each other some space for the time being. Focus on yourself, let him work things out for himself and once he does then maybe you both will get some closure

Closure is for accepting what has happened and learning from it and moving on, NOT forgetting bad behavior and starting over. You were wise to get closure, but you aren't ready to be friends, so don't force it. Stop the contact, and be happy with other things in your life, like REAL friends, and family, and activities that you enjoy, until you can recover from this failed, disappointing relationship, and have gotten healthier in the choices you make.

I think u shouldn't go back out with him, its just going to keep on happen like this, just stick being friends