What Causes Intermittent Pain In Upper Leg?

I have just begun experiencing intermittent hip pain in the right upper leg (ball and socket?). It comes in waves, but then can disappear. It quiets down with tylenol and rest. I am an active 70 year-old and have never had any problems with my legs, knees, or other joints. I walk about 3 miles per day, sometimes more. I also do balance and back exercises. I recently fell while walking and have started a pt program to improve balance. Lately I have begun walking faster. I also changed my walking shoes. Should I stop exercising to give it a rest?