Questions: Flirting

my friend and I share food or drinks every day. We don't need to ask and have no problems putting stuff in our mouths that was in the other's mouth. He picks food right off my plate and I bite off stuff he's eaten. He's fed me off his fork and spoon, he held it and put it in my mouth. He's put food in my mouth a few times, chocolates once and today he stuffed a gingerbread man in my mouth so hard I almost bit him. What's this about? He doesn't do this with any other girls. He's nibbled on my thumb once too and today I said "by whom?" and he asked "you want me to bite you?" I suggested squirting whipped cream we had for a project into each other's mouths and he seemed to like the idea.