OMG, IS HE CRAZY?!

So, their is this guy, and I guess you could call him a friend; I'm not really sure. Anyway, he's the varsity quarter back for the football team and the last few days hes been messaging me about bondage, and bondage sex, and it's beginning to creep me out a bit. When he first starting asking me questions about it I didn't really mind because he would just straight up say what he wanted to know and I would answer the question if I felt confortable with doing so. Well now... he's just saying really creepy things. Like for example this is what he put:: "lol ankles cuffed.. knees tied.. hands behind your back...you have a ball gag in" and that was just real weird and i told him it was real random, but then he said:: "very....or me tied to bed spread hands n feet with gag n blindfold." Its starting to get really strange. I have no problem talking about it to my best friend, but no one else knows except for her and now him, well a lot about what I think on the subject anyway. I sit RIGHT next to him in math class so this is starting to get EXTREMELY akward. How am I suppose to handle this situation?? Its really strange.