I don't see myself as a girl, or a boy – just Kirsty

We both avidly watched wrestling – something that I have since found from going to live shows – is a very male dominated interest. When I had a bath, I played with the Ghostbusters in the tub, and spent quite a bit of time under my mum's bed with a bicycle helmet on pretending to diffuse bombs like I was Bruce Willis in an action movie. Yes, really.

In many ways, I suppose I was a bit of a tomboy. But in others, I was a stereotypical 'girly girl'. I loved the idea of having my nails painted, I have a life-long love of bright and loud make-up and I still own the Cabbage Patch Kid doll that I had when I was small. Her name is Angelique Faye and she smells of babies. But, I digress.

Truth is, I have never seen myself as a girl or a boy. I'm just Kirsty; I like what I like, and I don't like what I don't. This has never caused me problems and has, instead, meant that over the years I've found some great friends of both genders, none of whom I categorise by their genitalia. Why would I?

The only time I'm aware I'm the only girl in a group of boys is when we're out in a club. My friends rarely ever 'pull', despite being really handsome and funny. I think sometimes it's because I'm there, whizzing around on the dance floor, potentially someone's girlfriend. Similarly, I can never dream of kissing a man in a club when I've got the seemingly 7ft tall Tom dancing beside me. I've never even wanted to, and so we remain single and happy in our nonsense.

Sometimes, people have assumed that I don't understand things such as football, based on my gender. I'm not offended by it, I just regale them with tales of my time as a sports PR, or when I went on Soccer AM with Peter Schmeichel, and that seems to stop them from talking to me like I have no knowledge of sport because I have boobs.

My gender has never been something that I've felt categorised by in adult life. In school, we'd be punished for being a naughty class by sitting boy-girl-boy-girl. As an adult, I've never been shunted into any gender box. Well, until this week.

On a Tuesday, me and two of my best pals get together to eat dinner, have a beer and watch movies. They both happen to be boys, and that's never been an issue – it's just not important.

But this past week when we were all watching a Netflix documentary, the Mixed Martial Arts (MMA) fan in our group invited the other boy in our trio along to a Ultimate Fighting Championship fight night taking place on the weekend before my birthday. I sat there aghast as he said, in all seriousness, that I couldn't go to his house to watch too, because I was a girl.

"No b****es allowed!" he exclaimed in his normal joking manner, and I assumed that he was pulling my plonker. He was not joking.

Though our mutual friend doesn't have a particular interest in MMA either, he was invited to this night in because he was a 'lad'. I was not being excluded because I didn't have a particular interest in the sport – I was being left out because I happen to have been born with XX chromosomes.

I want to say that this was not a problem for me, I could just stay in and do other stuff, but it really was a problem. It hurt my feelings.

What hurts more, I think, is how other people seem to understand and pass off this casual, everyday sexism as being commonplace. "Oh, it's just lads being lads", is a popular get-out clause to being bloody horrible for no other reason.

There's no way that anyone would stand for it had he invited me because I'm white, but left my pal out based on his skin colour.

You'd never excuse that kind of exclusion if it was based on sexuality. Had I been dismissed for being gay, or black, or disabled, it would have been completely inexcusable. To me, this is no different. I was born a girl, I didn't choose to be. So why are women still held back because of their gender?

'Lads being lads' is no reasoning for being horrid, is it? He's my friend, who makes an active effort to come round to share my food, go for beers with me, to discuss politics or religion. We're not honour-bound to one another, we spend quality time together because we just really like to. Why, all of a sudden, is the fact that I happen to have to do sit-down wees, a problem?

"It's just lads only," he said. "No women are allowed. That's how it's always been. It's nothing personal."

Well, for a long time corporal punishment was allowed, but they soon kicked that out when they realised it was a shoddy idea. As much as you'd like to think that it isn't personal, it absolutely is. Every day women are excluded from things based on their gender. Hey, there's still a problem with a fair wage at some organisations – with guys scooping more than girls in their pay packet. It's disgusting.

So now, on the weekend before my birthday, I'm going to spend the evening eating cake and watching wrestling DVDs with Angelique Faye while painting my toenails.

No human beings allowed, gender irrelevant.