What Causes Numbness In Hands Along With Headaches And Neck Pain?

Hi. My son is 14 years old, 5 5 and has not gone through his growth spurt yet (I am 6 4 and he has grown at the same rate as me.) and has been having loss of feeling in his hands. It generally comes on when he is exercising but can also come on when he is writing or even when he bends over and picks something up. He just had a test done to see if he has pinched nerves in his arms, but they came back negative. However his step mother had this test done years ago and her test came back negative and she had the surgery to move her nerves in her elbows and it fixed the problem. Granted hers was from years of typing. My father was anemic when he was younger and don t know if this is something that could affect my son if he is anemic. Is it worth having a blood test done and if so what should we be looking for in the results? He has also complained of his neck hurting and headaches now and again. The first time he ever had tingling in his left had was when he was a pitcher for his tournament baseball team. He also experienced shoulder and elbow issues. He hasn t played baseball for 3 years due to this issue. His shoulder doesn t bother him as much anymore but shooting hoops bothers his elbow and he loses feeling in his shooting hand (Left hand).