[mysty]

Lee doesn't like Casey in that way he seems like he was interested more in her physically or he's thinking he's moved too fast an realises he doesn't want a relationship an wants to pull away. Loads of men are like this an this has only happened since Casey told him to go to the bathroom which makes it clearer it was probably just the physical sense.
Lee's just being a man many men act like this come on really strong at the start then pull away and decide they don't want the relationship.