i (f18) have recently developed a FP (m19) who isnt my bf (m19) and i feel like its ruining my life.

i went to high school with my FP and knew him before he was my FP (i had a crush on him my sophomore year but it was shortlived and led to nowhere). about a month ago i saw him at a party and we were talking, catching up about life and stuff. a couple weeks later i consistently see him liking my stories on instagram and i hate to admit it but i liked the attention. he would occasionally slide up on my stories on snapchat and instagram and we began chatting as friends. suddenly i start feeling obsessed over him, wanting to talk to him more and wanting to hang out with him. despite me wanting to talk and hang out with him, i am only interested in being his friend as i am very in love with my boyfriend. but this obsession with wanting to be my FP's friend has gone farther than id like. he is the type of person to play games and joke around a lot and mess with your head. he will give me attention one second, and then leave me on read and it will drive me crazy. it affects my mood greatly. the times ive asked him to hang out in a group with me and other friends hes said no, but i believe this is because he is interested in being more than friends and would like to hang out with me alone. but again, i have a boyfriend and even though hes my FP, i dont feel comfortable hanging out with him alone. this rejection is devastating and i would really like to move past this obsession because, even though i have not flirted or anything to that nature, it feels like im being unfaithful to my boyfriend. my boyfriend knows him and i talk and is okay with it, but he doesnt know hes currently my FP. 

some days i tell myself i am over my FP and i am ready to move on, but once he likes my stories or messages me, the obsession comes back. what i am looking for is coping mechanisms for dealing with an FP, and maybe tips for getting over the obsession. any and all help is appreciated.