Problems

So me and my bf have been together for nearly two months (we’ve known eachother for 11 years, liked each other for like 3 years), and on valentines day we kind of showed that were together, now theres this one extremely popular girl in our class, has been school president several times, smart, shes actually pretty, and at the start of the year my bf and her started chatting, he only wants good or neutral relationships with classmates to avoid drama, and i’ve been fine with them talking, im not crazy like not letting him have girls as friends as long as theyre respectful of the relationship, the girl hs always saved his snaps and texted him often given reactions to funny stuff, but suddenly on valentines day when he posted me on his story, she went radio silent, stopped saving snaps stopped texting left him on seen even, he asks whats wrong and she gets aggressive saying “what do u want? U have a gf”, i have actually one other time felt shes too weird with my bf but brushed it off but this time i was quite sure she likes my bf, she never denied having feelings for him when he asked it directly, he has been keeping now a distance after i explained i dont feel secure in the relationship, although he still sort of keeps saying im probably misunderstanding the situation, but i know what goes on in a girls mind especially when she acts that way. Ive been feeling like i have competition even if he keeps saying he only wants me and hes legit been waiting to be with me even though he could’ve went ahead and dated prettier girls. Hes done so much for me and ive met his family, his relatives, and hes meeting my relatives soon and next week hes meeting my grandpa. Even with all of this i still feel like i could lose him, and so ive been just getting worse mentally, suggesting breakups but i promised i wouldnt, i just havent been the same ever since the girl acted the way she has, and she once threw a ball at me full speed while i was sitting. Im not sure how to stop thinking of her and go back to how things were when we hadnt gone fully public.