Having weird tingling on my left shoulder?

Well i was gone the whole week to staff for a camp and i've noticed that i have been having a weird sensation on my left shoulder. what usually happens is that i have a weird tingling feeling then it feels like it feel asleep then i can't feel it for 5 seconds then it comes back. i've told this to my parents and they think its because im just tired and i could believe that because i had to stay up till midnight when i was staffing, and i am really tired right now. So what could this mean does it mean i'm tired? or does it mean i have a back problem? or does it mean i'm just plain out crazy because this could be me being crazy. I really need to find out because tomorrow i am heading out for another week long camp.