What Causes Menstrual Cramps And Pink Discharge After Urinating?

I am a 63 year old female. Just today I ve noticed pink discharge on paper after urinating. No pain. Feels like menstural cramps. I did have kidney stones once about 10 months ago. Just had a GYN check up 3 or 4 weeks ago. No call of any problems. I did shovel snow for a half hour or so today. I ve done that before and never had problems. Any idea what the problem might be?