Why is my boyfriend's friend is weird around me?

my boyfriend lives with two flat mates. one of them has become a good friend of mine but one of them doesn't likes me. i don't have any problem with him not liking me but when it first bothered me i asked him straight way do you have some problem with me? he said neither do i like you nor do i hate you. initially i thought i am the delusional one but now if i am hanging out with him and his friends. whatever i talk for fun he tries to make it in a way that i am trying to harm someone by that or trying to break their friendship. he used to stare at my boobs too. once we all went out and he kept of taking my boyfriend away from me. later my boyfriend noticed it and then he also said the same thing. recently when we all went out he kept on staring at me weirdly. he once swore at me too. whatever i do he tries to make it against me and he keeps on staring at me weirdly i don't like it at all, the way he stares at me or his attitude. when my boyfriend wore my hair tie on his wrist he said such a lame thing you are doing. when we all talk i did not take his side many times instead took other flatmate's side. this time boyfriend also said he was looking at you weirdly then i told him throughout the outing he was staring at me.

Why is my boyfriend's friend is weird around me?
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