Help with ankle & foot pain?

I tripped over an upside down broken step 5 months ago. It was covered with the summer's weed growth & I didn't see it at all. So I fell at full walking gate with both hands full. My foot dragged across the step, & therefore overextended my foot & ankle. I felt the pain in foot, ankle, calf, & hip. I did the RICE thing, but the ankle has felt reinjured many times with even the slightest turn. I asked the dr about it last week & he confirmed it was just a sprain. However, now I am getting intense foot pain in last few days. It is achy underneath where arch meets ball & on top where u can bend toes up. Then at times when walking or just stretching I get sharp pains shooting across & through the ball & top of foot. Any ideas on why & how I can keep from reinjuring?