99% sure my Flatmate fancies me. What do?

I'm doing two semesters at another uni and moved in in January, so I'll be here till September. It's a mixed flat and everyone kinda gets on well, I don't dislike anyone including him. I sometimes hang out with them and sometimes with friends I have who also go to this uni.

He can be quite annoying though, I have the room next to his and he always keeps coming out conveniently just when I do, esp. at night or in the morning, this has happened like ten times now. He's one of those people who has a lot of friends but is a bit awkward, most of his friends are from the cosplaying and Quidditch society. Of course its nice to talk about what u do every day but he asks questions in a very interrogating manner which I don't like, and I'm pretty sure I've once overheard him moaning to another flatmate about how I "got in and went straight into my room" when I was back late and nobody was in the kitchen anyway, so it wasn't like I was being antisocial!! The other flatmate was like "OK, so?" Because I have a varied schedule I'm not up at the same time all day but I bump into him a LOT more than anyone else. He's made pointed remarks to me about how "sociable" he is before but he's actually really awkward sometimes and I have a lot of uni work to do so I spend half my evenings studying. None of the other flatmates have a ****ing problem with this.

He also keeps staring at me e.g. when our flat goes to the halls common room together, he'll be staring from outside the room. Last weekend my dad was in the city for a day so I went to see him, on my way back the flatmate was in the kitchen and I said hi, how are you as I was warming up dinner. I had a chocolate box with me that my dad gave me.

The flatmate was like "Fine" and then stared at the chocolate box and was like "Why do you have chocolates with you??" very aggressively. I thought this was weird and ignored the question at first and then said "Been up to much today?". Upon which he started stuttering "but w-why do you have chocolates with you?" and I told him my dad gave me them. He was like "Oh, I didnt know your dad was visiting, that's a nice gesture." I got the impression if a guy had given them he would have flipped out wtf.

TBH I would not say I dislike him but he's pretty ****ing rude and I don't like how pushy he comes off as. He's also a bit sneaky, I've seen him go through other flatmates' cupboards etc. to steal their ketchup etc. without asking permission, and I am 99% sure he nicked my washing powder but when questioned he started giving wishy washy answers so I gave up.

Just ask him about it. He may not realise there's a problem. He can't read your mind so best to be honest and ask - be nice but firm.

break off his legs