My Legs Feel Like They Are Swelling, As Well As

My legs feel like they are swelling, as well as my ankles. The one ankle between the ankle and akiles hurts and feels tender. I went to dr thinking I had a bladder infection and instead told me it was a bacteria infection and have been taking Flagyl since for 2 wks now. I am worried thinking it is my kidneys. I was in 5th grade and was hospitalized for 5 days. Not sure what is going on but I am worried. Should I go to the ER?