What Causes Severe Leg And Ankle Pain On Exercising?

I have been running for over a year now.. Lately I can run a good 2 miles with out any isssue. But the next day or so I can baraly make it a quarter mile. I have sever lower leg pain and ankle pain. I dont really feel exhausted I just can't run. My sprint is more of a jog at slow walking speed. I am a 25 yr old female. Is there anything I can do.