Im only fifteen and my bones make me feel about fifty?

i am fifteen in july, and right from when i was little i always had bone cramp in my knees? like where you cant move your knees and they sort of lock, you have to massage it and it really hurts :( since i have got older it has come back only worse and i get the bone lockings in more places than my knees, my back constantly needs a massage and it always aches, my body cracks and stuff when i move even if i lift my arm and its really annoying its embarrasing when people hear me clicking all the time haha. i just want a normal body that i can move about with without aching or hurting. my shoulder blade area is very bad for the aching and i am constantly rubbing them will i have a short life because of this :( x