I've had a stiff neck for three months, what do I do?!

I'm a 12 year old girl, and I've had a stiff neck for more than three months. No matter what I do, it never goes away. I've tried massage, heat, Ben Gay. Nothing works! It's really annoying since there is no one my age who has this. My upper back and the sides of my lower neck have been stiff for more than three months. Should I see a doctor about this?