I'm 18 Years Of Age. When I Start To Do

I'm 18 years of age. when I start to do any kind of work or exercise I experience prickly pins and needle kind of pain. starting from the head and then it spread down to the body. it inches and become very painful. today my skin turned red and splotchy. It get relief, I have to jump into a cold shower... I have had blood work done and my pc physician said nothing showed up. he left it at that...