I don't know what is wrong with me....

I'm 16 and am active in multiple contact sports. I have accumulated 2 concussions this year bc of these sports. (football namely) It seems like ever since I recieved the first one i have moments where i have this uncontrollable urge to pop my neck, and kind of turn my heads back and forth. Even now as I'm writing this I have done this act repeatedly. I'm starting to notice it more and more in my daily life, and even my fellow classmates notice me doing this. I don't know what it is and I don't know what I should do about it.

[catdaddy91210]

I'm just a 6'1", 152 lb teen that wants to enjoy playing sports while he can. I've already had multiple injuries that have caused me to lose valuable time that I'll never get back again. (dislocation of my left shoulder 3 times, and multiple broken bones) I'm afraid that if I find out what is wrong with me then I'll have to quit high school athletics.
Most of the time I feel like my body is deteriorating much faster than it should be. I really need an idea of what is wrong with me. Can anyone help?