Why would a ex ask if im seeing anybody?

Maybe he's trying to score points, and if he's dating/getting some he might see it as he's "winning". It sounds like he still likes you, and by not using your name, he might be trying to put you down. It's a weird male thing, acting like he couldn't care less when he could spend all night thinking about you. I hope I helped, if you have any more questions, ask me! I have lots of knowledge to give lol x