If the penis fits: The relationship compatibility factor most of us dismiss.

When it comes to a relationship, they say love conquers all… but can it really conquer a penis and a vagina who refuse to get along?

In my early 20s, I was in a relationship where the chemistry was like hairspray to a naked flame. We fitted in every area – shared professions, backgrounds, humour – except one very, very wide one:

Inside his pants, it was as if someone had chopped off a human penis and replaced it with a can of Coke.

The long and (not at all) short of it was this: we did not fit down there. Having sex was like that Friends episode where Ross and Rachel try to get his sofa upstairs: stop, start, forwards a bit, rest, pivot, back out, try again. (And that ends with Ross sawing it in half).

It was impossible for us to be spontaneous because the deed involved an arsenal of condoms and lubricant. We had a position repertoire of, um, one – me on top – as that was the only way to ease the damn thing in. And when it was in and the sex actually ripped me (which it did pretty much every time), I could see it doing the same to his self-esteem. After nine months we both admitted defeat.

Watch the Mamamia team reveal their most awkward sex stories below (post continues after video).

My heart broke; my vagina was sympathetic for two minutes, then did a victory dance.

But it’s funny that when it comes to weighing up our compatibility with a partner, we give less importance to our sexual fit. We talk about being the perfect height match, having the same schedule preferences (morning people or night owls), liking the same bands/politicians/schools to send the kids. But we have an, ‘Oh it’ll be fine’ attitude to whether our genitals – organs that are actually physically going inside each other – are going to slot into place.

American TV show host and former-model Jenny McCarthy brought the issue to light (ie overshared majorly) when asked about her marriage to New Kids On The Block singer Donnie Wahlberg. She replied, “He has the most beautiful penis I’ve ever seen […] it fits my vagina perfectly.”

OK, try to get past the ‘beautiful penis’ bit (anyone else imagining a bronze cast on the mantelpiece? A photo in the family album?). Anyway – she raises the valid point that being compatible down there is every bit as important as being compatible in your head. Sex isn’t a one-off event to get through – like, say, jury duty or chicken pox. You want to be doing that bad-boy for the rest of your life – and enjoying it.

Sure, you can improvise and make the sex (kind of) work. There’s non-intercourse fun. But, believe me, there WILL come a point when you just want to fuck.

And, wow, when two people do piece together – like the perfect sexual jigsaw – it kicks the buzz of having the same CD collection right out of the window.

So while I’m impressed at my 22-year-old self’s endurance, I would tell her to get out much quicker.

(Ideally before she got cystitis and thrush at the same time. My vagina and I are still making amends).

One, because you never want to get to the point where sex is something you or your partner dreads. And, two, what doesn’t fit you is likely to be the perfect jigsaw-fit for someone else.

What do you think? Is how you get on in bed as important as how you get on out of it? Does the perfect sexual fit exist?