Luke is right. Worn to the bone.. look at the runners in a marathon, they are worn to the bone by the end of the race. An old pair of shoes are at the end of their life, they are worn to the bone. You are emotionally stressed out, probably worn to the bone.

This sounds a bit unusual to me. "Worn to the bone" is most similar to this phrase "wearing your fingers down to the bone" which means working or practicing a lot at something. So this sentence means roughly "you must be tired"