What is his problem ? i dont get this ! HeLP?

Theres this guy hes a freshman star quarter back and he's really popular. he's in my homeroom and some of my cles. last semester him and his friends would tease me and make fun of my saying they smell , and there sweaty and other mean stuff im (5'0 && wear a 36DD). i never been rude to them and i carry myself like a lady , im very much a girly girl. So anyway after him and his friends were thru with makin fun of me he would stare at me and when i catch him sometimes he would look away and sometimes he would keep staring.. this semester his main friend started being nice to me and friendly idk why, his friends dont mess with me anymore theyre actually nice to me .but he still talks about me sometimes.. and he keeps stareing the whole cl period,, when the bell rings he waits for evryone to leave and im usually the last one to leave , so he always ends up walking behind me.. i though he was cute but he's a very disrespectful guy , a real SHOWOFF !and i dnt like him..why does he do this ?