I get chills/goosebumps (back of my thighs)it kinda hurts from how strong it is &when I get that I feel way to tired like I cant do anything but sleep?

Muscle tightness? It's not clear from your description what is going on. But are you feeling muscle tightness with tenderness in the back of your thighs? Have you been participating in sports or strenuous exercise activities where your hamstring muscles are very active (jumping, skating, skiing, for example)? If so, your symptoms may be from muscle tightness, and may respond to local heat. Hope that helps.