Someone please help

So I have been experiencing what I think is bone pain in my left arm. It started out only in the upper arm and would only occur when I put pressure on it (for example: using ski poles to push myself) the pain was so unbearable I would have to stop, thus loosing momentum and having to just push through the pain. But recently I have been experiencing it in my whole arm. From the back of the shoulder to the finger tips. It almost feels like I am unable to move my arm and the pain is excruciating. I can hardly talk and I usually start to cry the pain is so bad. The only thing is that I haven't had the pain long enough for my parents to be worried about it. But I hurts so bad.

By the way, I am 16 years old, and have never had an injury in this arm or shoulder.

Can someone please help me. I'm not sure what could be wrong or what I can do.