I was treated for chronic prostatitis along with e coli UTI a few months ago, but very little symptoms are still there, like frequent urination if I drink a lot of water. From a few days I'm noticing Bubbles in urine. The bubbles are more in morning, and sometimes in evening also. They go when I drink a lot of water. I went through creatinine test, ultrasound KUBP, urine routine and culture three months ago. They were normal. What should be the cause?