One minute, I'm ambling down the street wondering whether I can justify buying another croissant, the next I'm yelping in pain and barely able to walk.

All of a sudden, something in my hip clicks, and it suddenly feels like one leg is longer than the other.

Effectively, it is. The hormones which make the pelvis stretch for childbirth can kick in early once a woman falls pregnant, and the hip bones can easily displace. I am among one in four women to be affected, to a lesser or greater extent, by Symphisis Pubic Dysfunction (SPB), which, in my case, kicked in after just eight weeks of conception.

At first, I thought it was unlikely to be related to my pregnancy, precisely because it was so early on. Some bad advice from a midwife reinforced my belief that it was some other cause, but a flick through an NHS hand-out revealed a whole section on the condition, with the warning that it must be caught early to avoid long-term mobility problems.

Now, the pain comes and goes. I walk less than I'd like to, instead trying to get my exercise from swimming. It kicks in when I least expect it, and suddenly I'm hobbling along slowly, and calling my husband to come and pick me up, despite only being two blocks from home.

It's a pretty shocking feeling for a reasonably fit 32-year-old to suddenly be rendered virtually incapable of walking. The only movement I can muster is the kind of shuffle which would qualify any elderly person for an offer of help crossing the road.

The specialist physiotherapist taught me pelvic floor exercises which apparently help. I've been offered a supportive belt, but I'm trying to manage without the bulky device. There's enough of me already.

The condition is just one of the many surprises for novice mums-to-be such as myself. Of course, I'd expected the expanding belly and the sleepless nights, but I'd understood I'd be joyously eating for two with abandon, not having to reduce my meal sizes because of intolerable bloating.

I'd also expected the odd affectionate pat of my rounding tum, but nobody told me that my whole body would become open to public scrutiny. All of a sudden, Facebook was awash with alarming proclamations on the size of the "udders" I would develop, with one friend reassuring me that it was all OK because my breasts are "no longer an object of sexual desire – they're functional". It did little to make me feel any better.

Clearly, the pelvic condition is a hindrance, but all things considered, I do feel I've been fairly lucky so far. I didn't suffer any sickness, and, despite my relative ignorance, I had a pretty grim expectation of nine months of hell. Instead, I find I'm feeling quite spiritual about the life which is developing inside me, which almost, but not quite, compensates for the lack of alcohol and soft cheese.