Notice here that even though Simon is obviously intoxicated, he still groups himself in with classmates like Leah who don't partake in adult things like alcohol and sex. This again highlights that drinking isn’t something he particularly wants to do, but he bends to the pressure to be cool and fit in with his classmates. Also, the fact that Simon thinks of himself as someone who doesn’t drink—even though he’s currently drunk—suggests that he’s not fully aware of the changes he’s going through.