Sometimes when you have a bowel movement, if it's a big large one, it will rub or put pressure on your prostate and seminal vesicle as it gets the feces log passed it, this will essentially make you seem to sperm but because not all sexual organs are involved, such as your testicles and **** etc, it will mostly be semen but without sperm in it, this is normal and it won't feel like an orgasm. I do this quite often. It just depends how big your log is.
It's nothing to worry about. It happens sometimes when the hard stool presses on the prostate.
So long as it's clear or white, there isn't any pain, burning, blood, etc., it's okay. You might want to increase your water and fiber intake to avoid the hard stool, but this isn't anything to worry about.