Soiled myself in Primark changing rooms

I was out in Primark today in Peterborough and when I was trying on these trousers, I released what I thought would be a fart but unfortunately I felt too much moisture afterwards and I reluctantly checked to see if the worst had happened. Yep, I'd pooed myself, and there was a small stain on the new trousers that I hadn't yet bought. I was incredibly embarassed and shocked (who wouldn't be?) and just didn't know what to do. I panicked and stupidly put my trousers back on and replaced the new trousers on the rail and walked home and I was almost crying. Is this common? It has never happened to me before and I feel soooo stupid. I'm trying to think why it happened and I haven't eaten anything out of the ordinary. I just wanted to tell someone because it's making me feel incredibly stupid - I'm 20 and I pooed my pants - but I can't tell anyone I know because I'd never live it down.

Please don't make rude comments this is really getting me down, I just need reassurance that I'm not some freak! Thanks.