Experience: I didn’t know I was pregnant until I went into labour

I was 20 and working in a shop when, one Monday afternoon, I started getting stomach pains. I assumed it was to do with the medication I was on; about a year before, my periods had stopped and I had been in and out of hospital to find out the problem.

I’d had blood and urine tests and endless scans. I was told it could be endometriosis or cancer, or that I might never be able to have children. I’d had aches and pains, felt tired all the time and had stopped drinking because it made me sick. The doctors couldn’t find anything wrong with me.

Two weeks earlier, I had been to see a gynaecologist, who gave me internal and external examinations, diagnosed a pelvic infection and put me on antibiotics and hormones.

After I had struggled through my day at work, the pain kept me awake all night. The following morning, my mum took me to A&E, where a doctor asked if I’d ever been given a pregnancy test. I had no idea because I’d had so many tests by this point.

I couldn’t believe it when the test said I was pregnant – I even asked them to do a second one. I didn’t think it was possible, having seen the gynaecologist two weeks earlier.

Soon enough, they were moving the ultrasound machine around my stomach, saying, “There’s the head, there’s the neck.” That’s when I saw this baby appear on the screen. The doctor estimated it was at 42 weeks. It was their way of telling me I was in labour. Once I realised what was happening I was in bits; I had no idea how I would cope. I thought I’d ruined my life.

They did a great job of keeping me calm but because they had none of my medical records, they were wary of administering an epidural. All I had was gas and air. After a long 12 hours, I gave birth to Charlie.

My mum had a panic attack when she found out, but it was more relief than horror. After spending so long worrying what was wrong with me, my main feeling was delight that I was OK – and my parents felt the same. Mum was with me all through my labour and when she rang my dad, she asked, “Are you sitting down, Grandad? Michelle’s having a baby.” They got their first grandchild ahead of schedule, but they were so happy.

My phone was out of battery when I went into labour, so I couldn’t contact the father, Gavin, straight away. My dad had told all the neighbours, so Gavin rang him and asked if it was true, and if he was the father. Dad said yes. We weren’t officially together but we had been seeing each other a lot; we met at the local sports club. He panicked when he first found out, as all of us did, but once he saw Charlie, he immediately fell in love.

I was kept in for observation for five days, during which my mum went to the shop where I worked. My manager donated a whole trolley of baby things. People were unbelievably generous; somebody even gave me a pram and a cot.

Once I was out of hospital, Gavin and I got together properly and he moved into my parents’ house with us. The idea that I was a mother didn’t sink in for a long time: I suffered postnatal depression as I hadn’t had time to adjust. It took me nine months to feel a bond with Charlie. I’ll never forget the day I felt a rush of love when I looked at him. Two years later Gavin and I got married.

We’ve had two more children since then. I understand it when people say, “How did you not know?” But I was visibly pregnant with my second two, whereas with Charlie I barely had a bump. He turns seven this year and he’s really healthy. That’s all that matters to me. I didn’t follow up with the gynaecologist or any of the doctors I saw in the months before I gave birth. Perhaps they just weren’t looking for me to be pregnant.

I always wanted children but I planned to wait until I was at least 30, with a solid job, a house and a husband. I just did it in reverse order. But I believe it happened for a reason. It made both of us more motivated. What we did was no longer for us – it was for Charlie.

• As told to Megan Carnegie

Do you have an experience to share? Email experience@theguardian.com