I just got my first boyfriend (I'll call him F) at the ripe old age of 16. He'd apparently had a crush on me since freshman year in high school and didn't have the courage to fess up until senior year. We talked for a few weeks and decided to pair up a couple days ago. I told one of my closest guy friends (S), since as far as I know, we don't have any romantic feelings for each other. When I told him that me and F were dating, he started answering in very short answers to my texts and IMs. He keeps snapping at me over petty things like web comics I don't like, how to hold a flag, how I don't like the anime he likes, and other stupid stuff like that. Before me and F went on our date, S was telling me that he was happy for me, etc, but once I told him that me and F were dating, he became very bitter toward me. How am I supposed to confront S about his behavior without him getting pissed at me? He's acting a bit childish for being 20, like someone took away his toy. What do I do now?