Guys why do you disappear and come back to a girl? why?

OK so why would a guy say talk to you text you pursue you, and say you hook up ( no sex, no oral) just make out, dry hump w/e. than he gets the idea nothing further. He disappears, become a bit distant if I text so I stop 2 texts max if he still has same attitude I back off. Than I hear from him again, full on trying to get me back, than I give in after a while same story? I know you'll say he just tried to get in to your pants didn't but I am sure he can get it way easier somewhere else for sure. PS. his ex cheated on him year ago. they went out couple of years. ... now I know he owes me nothing, we didn't officially date so I can't be mad but I do get mad? how do I even respond when he comes back? like be distant and just like nothing happened, or do I just totally not answer him. I do like him, and I get the point he has been hurt etc. but not an excuse. Now if say I wanted to kind of may b take a chance on him again how do I react in a way that he won't be scare and run away again. ( we do have like talks obviously I try get to know him, when he opens up a bit that is when disappearing happens).

out for a month and comes back.