What Causes Pain Around The Occipital Region While Exercising?

It seems that after i jog or do the treadmill, at some point , maybe after a week or 2 of excercising i start getting a pain in or around the occipital region. If i bend my chin down towards my chest it is very stiff and soemtimes get loud cracking noises. I usually stop excercsing for a week or so and then it goes away.