Oxybutynin prescribed after uti

I had my first ever uti a few weeks ago for which my GP prescribed antibiotics. The infection has cleared but I still have awful symptoms, feeling that my bladder is constantly full and needing to urinate every half hour or hour throughout the day and twice overnight. I can't go out for long and when I do I'm seeking out toilets I can get to. My GP has prescribed Oxybutynin for what she says is an irritated bladder. Has anyone else had this experience following a uti? Will I have to take these tablets for ever, or can it be a few weeks or months treatment? (My GP has arranged a repeat prescription). I'd be pleased to hear anyone else's experience of this situation.