We had sex and he was hard throughout and he kept saying he was "about to go" so I got off of him and went down on him. He started giggling and clenching his legs together and said "that feels amazing". We were both embarrassed because he was laughing. I tried this for about a good 15-20 minutes and it didn't happen. We were both surprised. Now he's complaining that his lower abdominal area is aching. Why is this?