I am 23, 5'7, 130 lbs, pescatarian. I try and run as much as my schedule allows (3-4x a week) but afterwards I always get stomach cramps and an excess of white vaginal discharge. I've been with the same person for two years and have had a pap and STD tests regularly (most recently last month), without any concerns. Is there a reason for this discharge? Or is it normal?

sidenote: I have a desk job that has me stationary 8 hrs a day. Besides the running and living on the 4th floor, I don't do much more activity during the week.