Mine happened when I was about 17. I was with these two girls, both older and far more experienced than I. We were on a haystack playing around, very soon we were naked. We had sex then the two girls jumped on me ( to be honest I did not put up much resistance!) One sat across my face the other my legs. Then she got hold of my balls started playing with them and squeezed hard. When I opened my mouth to yell the other pissed into it! Since then I always enjoyed all sex, particularly if a bit rough.