What do you do when your son throws a tantrum in Waitrose?

Something quite incredible happened when I had my first child. Like a brain transplant took place at the moment of delivery and I became a very different person.

Lots of people told me this might happen. “It changes you forever,” they said.

But I was too busy living another life without sleep deprivation, limitless love and a belly full of stretchmarks, to listen. So how did it change me?

Well for every woman who gives birth then sinks back blissfully into the pillows, there are scores like me who sit bolt upright, eyes wide and think: “What have I done?”

For me, this was not because she wasn’t perfect in every way. And not because I didn’t adore her from the top of her down-covered head to the tip of her tiny toes.

But because with her, came a big dollop of confusion and a mountain of seemingly insurmountable obstacles and challenges.

And she didn’t make me feel “complete” as many promised she would.

Believe it or not I am not so much the exception as the rule here.

A recent survey questioned four thousand couples and discovered that children, up until the age of five, make mothers feel less fulfilled and content with their lives than they did when they were childless.

I think this is partly to do with the change it brings – not just to life, routine and sleep to wake ratio. But to your very being.

I was a different person because of my daughter’s existence.

Once brave, I was now afraid. Tormented with anxiety in fact. I was no longer spontaneous. I was a planner. I yearned to be with her at every second. But I craved time, silence, freedom, peace.

I felt happier than Pharrell Williams. And more miserable than Morrissey. I was never alone and yet lonelier than I had ever been.

I lacked the clarity and confidence I once had in bucket loads. But I gained a selflessness and generosity I never had.

I felt exhausted, deflated and really quite confused a lot of the time. But I became more patient, more resilient, more tolerant.

When you are pregnant with your first, other seasoned mummies talk about motherhood with a sugar coating.

Those rose-tinted, soft-focus, beautifully blissful whisperings. Promises that for every moment of tiredness and exasperation you will get ten more of harmony and happiness.

“It’s unlike anything you have experienced before,” they say knowingly.

“Enjoy every moment. They grow up so quickly,” they add sagely.

I am not one of these women. As a fan of brutal honesty, post partum I always vowed to tell the truth about giving birth and being a new mum to any pregnant woman who asked me.

I saw myself as a one-woman vigilante, going into the world, righting the wrongs of mums who had gone before. “Does it hurt?”

“Yes.”

“Will I get my flat tummy back?”

“Probably not.”

“Will I ever feel sexy again?”

“Unlikely.”

“What’s the secret to being a good parent?” one friend, expecting her first in a few months, asked me recently. “Don’t kill them,” I said.

She laughed. “I mean it,” I said deadpan. “You’ll want to, but don’t.”

I’m not sure she will ask me for parenting advice again.

But here’s the thing: child-rearing is not always a magical gift full of love and joy.

There are times when your heart is so full of pride and feeling it could burst. You can’t imagine your life without them.

But there are other times too. Times many mothers like to pretend don’t exist.

Angry, frustrated, exhausted, baffling times.

Times when you want to shut yourself in the pantry and compulsively eat crisps.

Times when you could happily sprinkle a bit of Prozac on your Special K to get you through another school run.

Times where you feel like throwing your espresso at the nearest wall and then punching your fist through the brown stain.

Times when you are so mind-blowingly bored you would rather watch paint dry.

Times when you wish you could evict what is surely the world’s worst houseguest.

I’m not a bad person. Honestly.

This is just some of the things I wasn’t told about motherhood.

And here’s another: becoming a mum is one of the best – and worst - things that can happen to you.

Now, I was reared in the generation of women who were told we could be anything we wished and succeed.

What I didn’t count on was that motherhood, something that is supposed to be biological and natural, would be the most challenging of any of the choices I have made.

As it turns out, just because you can “have it all” doesn’t mean you will be instantly good at it.

And this can be hugely deflating.

When I had my daughter and did not find breastfeeding to be the peaceful or pleasurable experience it was advertised as, I felt like a failure.

When my son had his first temper tantrum in Waitrose and I flapped around him trying to stop the wailing, I felt like a letdown.

When my neighbour found me hosing him down on our front lawn after a major potty training accident, I felt like a disaster.

And when my daughter had to have an operation on her eye at five years old I felt helpless.

But parenting is like a participation sport - you get better with practice.

Yes, becoming a mother is a seismic shift. You do change. You have to.

But when you cross that threshold, walk through that door, you don’t ever look back.

And for every hideous moment I have encountered, I have never once wished I wasn’t a mum.

So really, my “truth” is no better than any other mother’s refusal to betray the negatives to anyone not already “in the know”.

Because none of us can really tell you what being a mother is like.

Just like we couldn’t explain the gut-wrenching, heart-stopping, exhilarating peaks and troughs of a roller coaster.

And actually it’s probably this blissful ignorance of breeding that makes you join the ride in the first place.

@EllenWiddupRead more from Ellen here