Guy's Behavior

Why does he annoy me on purpose? How to make it stop?

Hi, this is a really long backstory so please be prepared to read a ton. My relationship with this kid is weird. (In a sense that I don't even know if we're friends or not). He is my friends step brother and has only been going to my school for three months since he moved here. He's joined our friend group so I see him every morning and we all eat lunch together also. When he first moved here he added my best friend on snapchat and started flirting with her every day for like a month til she friendzoned him. Then I added him and we started talking as FRIENDS. I caught feelings and told him which I now know I shouldn't have done since I knew he felt different, but long story short we unadded each other on snap and don't talk out of school at all anymore unless we go out to do something with our friends. Now whenever we talk its only making fun of each other in a not flirty way like I mean he treats me like shit so I return the behavior. But now every day at lunch for the past week I'll be minding my own buissness and he'll start throwing things like food or rolled up balls of paper at me. Not to hurt me but just to get on my nerves I think. I tell him to stop everytime he does it but he just laughs and I'm over it. its annoying as fuck. Why does he think it's ok to throw shit at me and how do I make it stop? He's sixteen and has was in juvi a year ago, just to give y'all some background on what this kid is like. Please help it's so annoying I don't know what to do anymore.
Why does he annoy me on purpose? How to make it stop?
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