When I take tests, or exams, my shoulder and back start to get very stiff and I constantly have to stretch my neck and arms just to feel a little relief. I'm not that old, I'm still in high-school and my mother gets shoulder pains as well. What can I do to treat this and make it feel better?

Most likely it is caused by test taking anxiety.

Also, it could be caused by the way you sit and bend over the test paper.

That and tension

I think you see doctory or taking some pain relief like pain o soma, carisoprodol 350mg etc.