Rear Heal Pain

I have sometimes severe pain in the rear of my right heal.
It tends to lessen as my activity increases, but is more severe during periods of inactivity.
The pain seems isolated directly in the rear and below my shoe line.
When I press on the area, it increases the pain.
I thought it was Achilles Tendonitis, so I laid off of activity for over two weeks.
However, it did not imporove.
Please help me.