I have a haorrible pain on the back lower side of my right leg fron the back of my knee to my heel it is tender to the touch it hurts when I walk?

Calf pain. Is the calf hot, red, swollen? You may have a venous blood clot or an infection of the skin. Both should be checked out at once for proper diagnosis & treatment.
? DVT. Better get checked to see if you have a blood clot. Ultrasound will make the diagnosis.
Worrisome. Any pain down the back of your calf that is tender to touch and hurts when you walk should be checked out. Any horrible pain anywhere should be evaluated. Two goods reasons to seek attention. Your symptoms are worrisome. This could certainly be a dvt.