At the end of 2011, party season was under way but I was in no mood for festivities. Two years into fertility treatment, my body was pumped full of synthetic hormones and felt like a pin cushion, while my head was filled with both the fragile hope of having a baby, and the exhaustion of failed clinical attempts to do so.

I was in my late 20s. I met my husband when I was 22; we got married when I was 25. “I want to have kids young,” I’d told him. It was a feeling I’d harboured since my teenage years. But I’d also had the nagging sense that it might not come easily to me. As it turned out, my intuition was right. Approaching 28, I was a regular on the infertility merry-go-round.

I was recovering from my second miscarriage that year when I heard Sia’s raspy voice on the car radio belting out words that sounded emotionally weighty for an electronic dance number – her David Guetta collaboration, Titanium.

It’s not a song I would have necessarily rated or listened to again – I’m more likely to play 00s R&B and hip-hop – but it came at the perfect time in my life. I had forgotten how days felt before fertility drugs and the diarised cycles of administering them. I’d been constantly wearing a brave face and cramming in hospital appointments before and after work, going about my job through a fog of longing and hormones. It had left me in a “cry on the bedroom floor” kind of a heap. I needed something to drag the hope back into me.

I turned the radio up and listened to the lyrics: “I’m bulletproof, nothing to lose / Fire away, fire away.” It felt as if it was talking to and about me, issuing a riposte to all those shots of disappointment that had been fired our way. As Sia’s vocals ascended through the chorus with Guetta’s soaring synths – “Ricochet, you take your aim” – I cried, but I felt myself gaining power with her, too. “You shoot me down, but I won’t fall / I am titanium.” Those were the words I needed to hear.

I felt like a puppet pulled upright again. I streamed it on repeat in the days that followed. I might not have been able to face the work Christmas party but I wasn’t going to languish on the bedroom floor any more.

Over the next months, I spent a lot of time in my car, travelling to work and to fertility appointments to get my blood tested, hormones measured or insides scanned. Listening to Titanium became routine. Each time, its cinematic surge had the same empowering effect and I’d turn up the volume, wind down the windows and defiantly sing along in my terrible voice so it could wash over me.

The following May, when my husband and I headed to the clinic for another IVF embryo transfer, I let it motivate me; when we drove back from scans confirming we were six weeks, then 12 weeks pregnant, I celebrated with it. As I nervously made my way through my pregnancy, I turned to it when I needed the boost.

In January 2013, our first son was born. Today, he is the eldest of three: his brother arrived 15 months later, via IVF too (the last of our fertilised embryos) and four years later, another brother, without fertility treatment. We consider ourselves unspeakably lucky; for many, the outcome is not the same.

In our family, everyone knows Titanium is my fight song. It’s the only big commercial dance hit on my playlists, and a marker of something I overcame.

My kids call me in whenever it streams or plays on TV. When I made my husband a playlist for our 15th wedding anniversary, it’s the song that represented our 2011. And the other week, when he was out with friends, he sent me a voice note from the bar: he’d recorded it playing in the background.

There’s something all-consuming about fertility treatment: you view life only through the filter of your efforts to get pregnant. If you’re lucky, the filter lifts. It did for me, but the fight song remained. So, now, elsewhere in life, when I need a shot of strength and find myself alone in the car, down goes the window and on it goes.