It's a natural response for the male to go to sleep after having an orgasm. That's not just a sexist remark - it's a medical fact that all sorts of chemicals are released are released in the brain at the moment of ejaculation that have sedatory effect, which is why it is so commonly used to help with getting to sleep.
I masterbated & had the BEST orgasm the other night ago.... after I came, I could feel another one coming on & the last thing I knew I was asleep & woke up to find a big wet spot.... gotta love vibrators<3