After masturbating this morning I had severe stomach pain and was eventually sick, then went to the toilet afterwards and it wasn't until then that things went back to normal. I have had stomach pain a few times afterwards but never this bad.. have never been sick and had to go to the toilet to feel better. What causes it? Is it just being vigorous, or holding one's breath during masturbation? I don't have burning pee or any signs of an infection.

Thanks.