I know this is the girls locker i'm not sure if i'm allowed in here but here goes!
Okay first off, if he really remembers everything you say or your conversations, sure it means he has good memory, but what else does it tell you?? He listens. When a guy listens, he is interested, when a guy doesn't, you'll get an occasional eye glance and a short response. Trust me!
If he is teasing you about little things, and you both can laugh about it, thats a good sign lol.

It probably means the things he makes fun of you about, he thinks are cute.
What you should do is try and read all the signs, like what kind of stuff does he bring up weeks later? And would it in anyway have anything to do with you 2 being in a relationship!
Good luck =]