Most Helpful Guy
You absolutely have to ask him why he wanted to stop seeing you... he alone can tell you. It could be anything from him having met another girl, to him having decided you're not the right one for him... up to even just an emotional decision which he felt sorry for 10 min afterwards but didn't dare to come back to you.
Just be nice to him and ask him. That will at least remove the uncertainty and you'll know wether friendship or even more is still possible :D
Most Helpful Girl
He either wanted to stop before it had a risk of getting serious, wanted to pursue someone else, or was just being stupid. Either way, it's best to not worry about it and just find someone else to hook up with =P