Physiologically, a man’s erection is strongest while standing up or leaning forward due to a little thing called gravity. When your penis is below your heart, blood flows faster and stronger to your little soldier. In essence, your penis has high blood pressure. Having sex on your back causes a few things to happen:
Your penis becomes much closer to “heart level” thus reducing penile blood pressure, causing a softer penis.
While your woman is riding you, the pressure from her vagina squeezes the blood out of your penis, and although it feels amazing, she is literally squeezing the fuck out of you.
Blood flow is further diminished by her weight on your central body. Even though your mind is telling you that watching a naked girl ride you like a sexy cowgirl is amazing, her legs are reducing flow to your lower body, further exacerbating the issue (this is also why you will sometimes notice cold toes after sex too).
It all really boils down to gravity. Blood likes to flow downhill, and having sex in this position is like trying to push it uphill, but never fear, hope is not lost; there are ways to keep it up. Try some of the following tactics to get her riding you again.
While you are fully aroused, put a cock ring on right before she rides you. This will assist keeping your penile sphincter closed, helping to hold the blood in your penis while her vagina is trying to squeeze it out.
it could be performance anxiety. believe it or not some men feel very pressured when it comes to sex simply because of, she not moaning, or she doesn't look like she's into it, I'm dong something wrong, maybe I'm not doing something enough, am I big enough <- this is a big one because its basically what woman constantly say they want. (not all women) but because now a days its all about size for most woman the little guy gets in a pickle. but thing on his mind don't have any sexual thought to them. he could be under a lot of stress. believe it or not, he can be in bed with you and be thinking about bigger issues in his life. even though sex is supposed to be stress relieving.
Your not the only one hehe, it's happened to me too! Don't you hate that! especially when your about to orgasm hehe. Well they say that it's because they were drinking a lot of alcohol prior to, and I guess that's what happens. Stay away from alcohol!
yeah don't you hate it when your male robots don't function perfectly... ?
There are many variables that could cause this with Pot and Alcohol are two perfect examples. Other things can also be blamed, thoughs straying to something other than being with you.
Scroll Down to Read Other Opinions
What's Your Opinion? Sign Up Now!That's not normal... I've never had that issue unless I've already orgasmed. After that it's hit or miss for 10 minutes or so before things go back to normal.
If they haven't already orgasmed it may just be performance anxiety. Maybe you need to get into it more, let them know they are doing amazing, moan louder, take control, etc to build their confidence.
were any of them drinking alcohol before the sex?
cause we are just human. so are you. humans have imperfections, and flactuations. the bloodflow is affected by many factors. both internal and external.
It happend to me once on a rebound just after my ex of 4 years broke up. I the realized that I don't feel anything for the girl and that was such a turn off that I went limp.
I've never had that happened to me before, that would be such a huge diss to me if it happened to me.
haha this answer is funny maybe it not the guy ha ha I get it
Sexual Relationships 
Sexual Health 
Most Helpful Guys