To all the men reading this:
If you identify with the reasons stated below, please listen. I’m saying this out of genuine concern for you as a human being: Go see a doctor. It’s neither normal nor healthy for your junk to hurt when you assume a normal sitting position (and I say this as someone who hates sitting, period). You might have cancer, or a particularly nasty STI. A few (very very small percentage) of you might actually have abnormally large reproductive organs which makes sitting (or maybe even standing) normally difficult. I feel for you — maybe consider surgical options?