How to know a guy likes you?

ok so im only in middle school. and theres this guy that i think likes me. two of his friends told him that he liked me and that they were serious but i told them that it wasnt true but i still wondered also he always saws that my art and my handwriting is beautiful. I have every period except two with him. We hav small fights sometimes but they usually only last for five minutes also one time when he got me reallly pissed because i forgot to do something in my project and i had to put something in it and reprint it (this happened in 1st period) he started to tease me really meanly. So i got his hw from my folder, i had stolen it from him but he doesnt care cuz he nos i always give it back at da end of the day, showed it to him ripped it crumpled it into a ball and threw it at him. He know that he had just gone over the line. Then i didnt talk to him and no matter what i pretended he wasnt there. Then in 2nd period he sits rite behind me. so he passed me a note that said that he was really sorri and that i had given him alot of stress from the times i was mean to him and that it just piled up and he said that if i needed help with the project hed help me also he asked if we were still friends and i wrote back yes so we get into fights but we quickly resolve it. But i know that he likes or used to like my best friend. Though 4 some reason when i pinch him or grab (and this is just playfully doing it) him really hard he says it hurts alot and starts whining. Though when i did it to my other friends there like "U no that i doesnt hurt" and i tell them back that i know that. So im not sure if he just wants to make me think i can hurt him or if he really is hurt cuz when i do it to my friends that are weaker then him they still feel no pain and also hes very sweet and nice to me so does he like me or is he just a friend