I was diagnosed with mono a couple of days ago and I'm drinking lots of water and resting but my pee is a very dark color, it's almost reddish/orange. Should I be concerned? Also I have no pain on my left or right side what so ever and the doctor said my

Here are some... It is okay as long as voiding comfortably, having normal urinalysis from properly collected urine, and having stable normal renal function. Otherwise, the color of urine may widely vary reflecting the degree of urine concentration and dietary consumption.
Best to have recheck. The urine color change is prob secondary to Mono, but it would be best to recheck with our DR. Make sure you do not urinate just prior to your DR visit as you will be asked for a urine specimen there for exam.