Did you every have whiplash? Did you fall off your bike as a kid and hit you chin on the ground? (I fell head first off my bike and knocked out both front teeth). If you have had any of these happen to you, likely you have headaches and neck pain. A simple exercise you can do to help with headaches is to do this:
1) lay on your back and put a rolled hand towel under your neck and bend up your knees.
2) nod your chin 1/4th of an inch like you are saying "yes" and hold.
3) do 10. slowly build up your hold to 5 seconds, then 10 seconds.