Help hat is wrong???!!!?

Using my friends account i need help. For the past few years I have had unbearable neck pain. It sometimes spreads to my left arm, my back and my shoulders. At least 10 times a day my neck will go very stiff and I need to crack it shock gives me a few seconds relief before the pain rushes back! I have always suffered really bad headaches and everything is just getting worse. I have had x rays on my neck and have been to the doctor many times but they don't seem to know what it could be. Also my knees crack when I stand up and when I walk. The x rays did not show any abnormalities. I am only 17, any ideas? Thanks in advance