I'm 16 and my back has always been tense since i can remember but recently my shoulder blades started popping and cracking when move them, pls help!!

Muscle tension: If these popping and cracking are painless, like when you crack your knuckles, it is probably nothing to worry about and they will go away in a day or too. If your tension in your back reflects very tight muscles, you need to learn how to stretch and or get a therapeutic (deep tissue) massage. If there is pain you should go in to a Doc. to get an exam. Physical therapy would help.