About 2 months ago I noticed a mild pain in my bladder and kidney area. Went to the doctor, she did a UA, blood work, and ultrasound. All came back negative. The pain went away for a couple weeks, then came back, and seems to only be in my kidney area. It is very mild and I hardly notice it, but I keep thinking it could be serious. 37 yr old male, 6ft 4" 260lbs. Any ideas?