I dont know what to do. Boy Problems. Help?

Okay. I am a freshman and ive liked this guy since the 7th grade. And all my friends and I thought he liked me too. I really like him but lately hes been acting jerky to me and is all over other girls older than us. He sits behind me in history. We actually chose our seats in the beginning of the year. Theres a part of me that wants to let go of him and another part that wont forget about him. I just dont know what to do. =/