Tissue in Urine Even After treating UTI

For the past year or so, I have noticed sediment in or tissue in my urine. It almost looks like the thin pieces of pulp like in lemonade or orange juice. I would later learn that my body was trying to fight infection due to a UTI. Sometimes, it would look like puss or stringy.

Recently, this turned into a bad infection where I developed fever and lower back pain. I was treated with Antibiotics . It cleared it up, or so I thought. Since then, I still see this stuff in my urine. Because I freaked out, I went to the doctor again, more than once, did some urine tests and cultures. Nothing. But when I did the home test, I noticed I had leukocytes. So my body is still trying to fight something.

I took D-mannose, which seems to help control it. But I have to take it twice a day it seems, otherwise, I will notice the stuff in my urine again. I don't experience any other symptoms really. Seeing this stuff in my pee has concerned me though. I am afraid that I will have to take d-mannose forever, which maybe is just covering it up, and Im not getting down to the root cause of this.

I guess I know that I am still fighting an infection, which likes to "hide" from the doctors and the tests, and then they don't get why Im in their office. I don't know what to do. I will keep taking the D-mannose, but, again, I don't want to become dependent on a product. I fear that the lining of my bladder is being eaten away slowly or something.

Does anyone have an idea what is happening with me? Could the d-mannose eventually just get rid of it?