Your probably okay. It seems pretty normal to me. Sometimes if I have a lot of discharge and it dries before I can clean it will kind of get stuck in the folds of my skin and come out sometimes. Hen you are moving things around because of masturbation then that could be it.
I have a confession, I watch porn. And in doing so I know that what you are describing is normal.
It's kind of hard to understand what you're describing when you call it a discharge in the title and then call it "solid white discharge" that is "not a solid cluster of white."
If it is not a flowing substance, it could be smegma, but there wouldn't be lots of it, I'm not sure how obvious it would be or what it would come off on such that you would see it. There are also discharges from yeast infections described as looking white and clumpy, like cottage cheese. Maybe that is what you're seeing?