Calf Pain – Unable to rest it

For 4 days now I have had pain in the middle of the back of my calf. The first day it was just above the achilles. The second day eased. The last two towards the top half of the calf. Sensitive to the touch for a span of about 3 inches. No apparent swelling or discoloration. No pain at all when sitting or still. Hurts quite a bit when I walk.Unfortunately I cannot rest it. I look after my very feeble 86 year old mother, and that I be on my feet and that I do some lifting.
What would you guess is the problem? And is ther anyway I can treat it myself. Thanks very much.