A guy i was seeing at the start of the year?

No matter how long you dated before if you felt somehing when you kissed him an don't stop him kissing you etc. There must still be a spark there. But just because things are better than before with headaches etc don't forget the person that he was when you dated him if you want to rekindle something. Spark doesn't always come along an hell it can even break your heart. But you have to follow your heart sometimes. I think he is interested if he spent the night with you an did things differently with you. Change is rare, but sometime's people change. Maybe you should hang around him a bit more see how he is now an take it from there.