What Does White Pasty Penile Discharge Indicate?

I discovered that I had a strange sensation of something passing through my penis. Afterwords I noticed a kind of pasty white substance in my underwear. As though it was a wet powdery material. What might that mean?
I weight 250 lbs, I am 63 with slight hypertension. I take an 81 mg aspirin daily.there was no sex involved.