I Am Passing Blood When I Urinate. A Couple Of

I am passing blood when I urinate. A couple of weeks ago, I was passing blood and was diagnosed with nladder infection. They gave me 7 days worth of antibiotics and the bleeding stopped. When I was done the antibiotics I started passing blood again. I used to get kidney stones when I had hyperparathyroidism, but I haven't had any since I had a parathyroidectomy. What do you think it may be? There is a lot of blood at times and none visible at other times.