Bilirubin Levels

Hey, I am a 21 year old male, with no previous liver/gallbladder problems in the family.  In late July of this year, I was having some nervousness and my stools changed colors to a yellowish color. I decided to go to the doctor, just to be safe. He did a blood/urine test and everything came back normal except my bilirubin was a little high in my blood test, and there was some bilirubin in my urine. From here, we had an ultrasound of my liver, gallbladder, pancreas, right kidney, and bladder. It all looked completely normal. We also did a hepatitis panel, which also came back perfect. My doctor told me to just come back in 4 months and get it tested again, and come back earlier if I had more symptoms. I don't have any jaundice or anything of that nature, and since then my stools have returned to their normal brown color after I got over my health-related nervousness. About 3 months after this, I went to the doctor just to have my urine tested again, and it showed no signs of bilirubin in my urine, so they told me to just come back in about a month and get my blood tested once more. It had been around 4 months since my first test, so I went back to a different doctor since I had moved, and had my blood tested again. They did a CBC, and a liver/kidney enzymes test. Everything came back completely normal, except for, again, bilirubin. The normal ranges (according to my doctor) are 0.0 - 1.0 and my bilirubin levels were at 1.7 mg/dL. Everything else on both tests was within normal range.  My doctor had given me urine test strips to just test at home randomly, and there will be about a 2 week period without any bilirubin in my urine and then a random day or two (maybe more sporadically) when there is bilirubin detected by the strip. What could this be? My doctor advised me not to worry about it because of my age and lack of any other symptoms, and said it isn't unusual for kids my age to have an "outlier" here and there and they usually work themselves out with time. Should I be more concerned? I had gained about 30 pounds over the course of about a year, and am now somewhat overweight, could this be somewhat of a cause? I'm starting to exercise a lot more and eat better, so I'm hoping this can help move me in the right direction. Any help would be appreciated. Thanks