What should I do? Ex-Boyfriend wants me back, sort of

I was in a relationship with this guy for about 7 months and it was great. We had some problems just like any other couple but we usually worked through them and communicated well. Then he broke up with me because he needed to focus on himself and he felt like I was a distraction and that I deserved someone who could give me more. Then about about 3 weeks later he texts me that he wants to talk and tells me that he wants me back and that hes going to be the man that I want him to be etc etc and we discussed everything that would’ve needed to change and that we needed to take it slow. Then about a month later he changes his mind again and ends things. I was heart broken again but once again a few weeks later he says he’s wants us to start over and to take it really slow and to be friends for a while and have “fun” together (I.e. continue to have sex while being friends) and we’ll see where it goes from there. I don’t know what to do because I care for him so much and I really want things to work with him. Apart from his indecisiveness, he’s an amazing guy with a great personality and work ethic and just a great view on life and we have amazing sexual chemistry. But I just don’t want to waste my time if it’s just lust that’s left with us or if all he wants from me is to have fun and he’s just saying “let’s see where it goes” so that I agree to be friends and have sex and do basically everything that comes with being in a relationship except the expectations and obligations. Should I do this? Should I be light hearted and just have fun and enjoy this time even if we don’t end up being together ever again? What if going slow is what we needed and this is when we do end up working out?

Any advice would be great!