It sounds to me like Cystitis. This is quite common, not realted to CAH, some people are just prone to it. I went through a few years where I had 7 or 8 cases, so far I haven't had one for the last 2 years! Treatment by antobiotics is the right method. I think you can help prevent it by drinking Cranberry juice if you feel any symptoms. I've had it quite often, even down to the bleeding. As long as you get it treated promptly when it starts you'll be OK.