[OMFG!You'reActuallySmart!]

It's understandable why he tells you to stop being a little girl because you used to insult him in the same manner, which only added fuel to the fire but now you can no longer take the heat. In other words, it fits the old adage (I'm para-phrasing), if you can give insults then you should be able to take insults.

The question of whether or not it's bullying comes down to what you define as bullying. I don't consider bullying to include saying or doing negative things to others. Instead, I consider bullying to be saying or doing negative things over and over to certain individuals with the primary purpose of hurting them. For me, the question becomes whether he wants to hurt your friends and you, or whether he's mostly joking. If it's the former, then he's a bully with an incredibly poor vocabulary who often is bored with his friends. Overall, it's probably not a good fit. If it's the latter, then he's an asshole with an incredibly poor vocabulary.

If you leave a bunch of friends due to just one person, it will imply those friends aren't worth as much compared to the one guy. It's certainly possible for him to be part of the group of friends but for you to not befriend him.