My dog (cavalier king Charles spaniel female 1 year and half) was spayed exactly one week ago. Soon after the spaying we noticed a lot of fresh blood in her urine. So we went back to the veterinarian who said it is probably a UTI and prescribed antibiotics. The next day the urine was clear. We felt relieved and thought everything is fine. Than the next day she had fresh blood in her urine again, a lot of blood. It looked like it was pure blood. So we went back and this time they said they did not know what it was and recommended we take her to a clinic to get more tests. She got her blood tested and she does not have problems with her platelets. They said that with the antibiotics, we can't test if it is a UTI anymore because the bacteria would not appear in the urine and also they said that it would be probably useless to do an ultrasound. They advised to keep giving the antibiotics and wait for a week see if it goes away. The following days there was still blood in her urine, sometimes a lot, sometimes less, yesterday her urine was clear and we hoped it was over but today it looks like pure blood again. She sleeps a lot but otherwise seems responsive, and gets very energetic when I take her out to pee. We have an appointment with a veterinarian who is also a surgeon for dogs in 3 days. I am very worried. Does anyone knows what could be wrong based on what I described?