What does this mean??

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So today I was walking with my best friend and I saw my crush/good friend. I told my best friend I would talk to her later and talk to my crush. We were walking to class and my crush says, "Hey can I ask you something?" I say, "Sure." He says, "Are you wearing a bra?" he's smiling when he asks this. I begin to cover up my chest. I say "no". Then he's like "Why not." I explain to him that I hate bras because sometimes they can feel uncomfortable and the underwire pokes me sometimes. He began to laugh and was like "I am so glad I am not a girl" I laughed. Before I went to the door of my classroom he said, "F*ck you" and gave me the middle finger and walked off. I called his name and I told him "f*ck you" and I gave him the finger as well. (Saying f*ck you.. is our inside joke haha) I just don't understand why he asked me if I was wearing a bra. He usually is calm and normal. I mean we joke around and stuff and make sex jokes because we are friends, but this was different. What does this mean?