Child Complaining Of Breathlessness, Pins And Needles While Playing Basketball. X-ray Normal. Reason For Symptoms?

Hi

My 15 year old active son has recently started having issues with exertion. During basketball tryouts and now practice, he starts to lose his breath and tells me that he feels a sensation of pins and needles in his chest area. His blood pressure is good and an x-ray shows nothing. I'm concerned as he has never had this before and he is more fit than ever. The exercise is hard but he's done it before. He looks stressed when this happens and is able to continue with a small break but still not at a level he is use to. We are waiting for an EKG. Any suggestions? No other health issues. Eats fairly healthy with occasional protein shakes. Drinks mainly water and almond milk.