hey doormouse! i used to get kidney stones on a frequent basis in my early-mid twenties (probably because I ate terribly, went out drinking frequently and never drank WATER :).
I had some success with the lifestyle changes the doctor suggested in order to avoid more stones. One big thing that makes stones popular with IBD patients is dehydration. If you're not getting enough water thru your kidneys, minerals (mostly calcium) will build up and give you stones. And it's summer so we sweat our water instead of it going thru our kidneys, so that may be hindering you too. Drink lemonade and lots of water, avoid salt and meat. And alcohol is a big no-no for kidney stone sufferers too.
I hope this helps if you hadn't already received the info!
Do your best, then to hell with it.
I recently got a urinalysis when I had pain in my kidney area, and it indicated I might have them: uric acid crystals in the urine. I promptly started drinking 2 quarts of water a day and the pain has not returned. I'm supposed to get an ultrasound but have not done it yet. General info: http://www.urologychannel.com/kidneystones/index.shtml
you might want to get them analyzed after they pass to see what their composition is. if it's mostly calcium, it could be due to your medicines, as other people suggested.