Alright. So... from reading this, You are obviously confused. And it makes sense. However, it seems like there is a lot going on... I don't know about the time frame in this, but I do know that it seems that he just isn't ready for a relationship. Most guys will tell you outright if they don't like you in a serious manner. I am sure if it was just for the sex, he would probably have the balls to tell you to your face. If he didn't, did you ask him? If you confront him about it and he blows it off or says something, or nothing...then it means it probably was. If he defends himself. Then it aint. Thats about all I got, Hope it helps.
The time frame is rather short I'll admit, from when things first started happening this school-year. And if he's never had a girlfriend or anything before, who knows what's going on in his head.
I am very bad at confrontation, but after everything happened I did ask him if he was just using me, and he looked at me and said back very definitively, "It wasn't like that." That was the only way he defended himself, but that was the only way I confronted him too.
One of me ex's blamed me for everything bad that happened in his life after we broke up and we tried to be friends but its just so awkward between us now and I dont like it. So you can either be his friend or try being his GF again and it could fuck up again.
Atm we're both just doing the friends thing I guess. However it's gone to how it was before anything got 'serious,' we're friends but going back to the playful-flirting thing again. I don't know I guess time will tell.