How to talk to girls better?

yeah, ive known this girl since 5th grade and now were in 9th.i like her very much and i have never told her.we have been friends-just not close one's.its always akward whe nwe are talking to each other.shes the kind of of girl who dates older dudes and isnt a virgin.see i am.and its just hard to talk to her.this year we have no cles together and she ran into me the other day and was talking about how much she missed me.thi is kind of weird but i have no armpit hair and am pretty sure i dont have the biggest "". i just dont want to be embarred.can anyone please help me. i think i love her.