Hello and thank you for asking HCM. I read carefully all your symptoms and concerns. There are a lot of reasons why someone might have blood clod in urine but since your ultrasound is negative,there are only a few left. The most common one is a UTI. So don t worry ,it can be treated easily. Usually a UTI has these symptoms, but it doesn t mean all of them. -A strong, persistent urge to urinate. -A burning sensation when urinating. -Passing frequent, small amounts of urine. -Blood in the urine (cloted or not cloted) -Passing cloudy or strong-smelling urine. -Pelvic discomfort. -A feeling of pressure in the lower abdomen. -Low-grade fever. Since your symptoms are gone after taking antibiotics, it means that you have a UTI and the medication is doing its job,like its supposed to. Feel free ti contact me any time. Dr.Endri Katro