my friends haring me what should i do?

im in marching band at my school and lately the guys have been making me very nervous. they do thing like slapping my *** and kissing me on the neck and i really dont know half these guys very well they sing to me and pet me on my head. they like to rub my legs and yesterday a guy even told me he wanted to make me bleed. these comments make me uncomfortable but i dont know what to do and i dont want to say anything to harsh cause some of them are kind of my friend what can i do to get them to stop. i will not stop band that is not an option. and i cant tell on these boys or theyll be suspended.