Us guys have to put up with are scrotum tightening or loosening depending on the temperature. For some reason, sperm production and storage is best done at a temperature slightly less than normal body temperature. So our balls hang low to keep cool, unless its cold, then they snuggle back up to us and stay warm.
But we can gain or loose an erection if we sit the wrong way and blood is restricted from flowing to or away from the groin. Could be the same with your 'junk'. Better or worse bloodflow causing it to shift, together with your intestines moving about *shrug*