Flank Pain 3-4 Mos,sometimes Right Side, Sometimes Left, Or Both.

Flank pain 3-4 mos,sometimes right side, sometimes left, or both. Noticeable any time, but more when walking up or down steps and moving in bed or in and out of car. Frequent urination, some leakage. My urologist diagnosed an enlarged prostate after DRE and PSA of 4.05. blood work is normal, history of stones, but recent CT showed only one small one and hasn't reached the urethra. Another CT with contrast dye and a cystoscopy are scheduled in two weeks.