What Causes Pain During Urination Along With Itching In Vagina?

I am a 19 year old female and I was having pain with urination and some itching discomfort for the past few days. Early this morning around 3am I started to see blood in my urine and also a bit of bleeding between the times I was using the restroom. I went to the hospital and was diagnosed with a UTI. Then I was prescribed antibiotics to clear it up. I took the first round at 7 am, and then again around 1. Now it is past 5 pm and I am still peeing blood. I have been doing so all day and the blood seems to be very thick with some clumps in it. How long will it take for the antibiotics to work? I have also had some mild pain in my lower left side. Why hasent the bleeding stoped and should I go back to the hospital?