UTI and bleeding. Know what's going on.

Two days ago I was taken to the ER because i had really sharp pain in my pelvic region and I began bleeding a little I thought it might have been an early period but the pain was so bad I passed out for a minute so I got worried. The doctors told me it was a UTI. I don't really experience any pain while urinating or notice a foul smell or blood even before the ER visit and after but they ran tests and couldn't find anything else. I'm currently on antibiotics but I noticed now that I'm starting to bleed again but it's like brown old blood. My urine isn't colored pink/red/brown so I don't think the blood is from that. I'm not sure if it's from the UTI or not my last period was on 04/03/17 and my cycle is usually 30-35 days so I don't know what's going on.