Why Does Sperm Comes Out Through Penis During Bowel Movement?

Sperm comes out thru Penis during bowel movelment? Hello, I m an unmarried man, age 22. Most recently when I go to toilet and try to press bowel movement, on the very first initial press before bowel comes out, I can see that sperm comes out thru my penis. It happens only once on each time I go to toilet. For instance say if I spend 5 minutes for bowel movement, it only occurs during first 10 seconds with first press to muscle. Any thoughts or suggestions, please?. I do NOT have any sexually transmitted disease or any other problem or any other issues with penis. And there is no irritation while sperm comes out. It just happens automatically even w/o the penis being getting hard. Also you know, I m not trying to get it hard during bowel movement. So it happens automatically. Any help or thoughts will be appreciated.