Hi
Sorry, not a guy again but just wanted to help. I have had 5 bladder ops so have experience with this more than I care to mention. Please take another test as sometimes when you are on other meds it can take some time for bacteria to grow & show infections also dont just rely on docs using a dip stick test for urine, get them to send it off to grow cultures. Secondly, drink lots of water & even tea/coffee as you will flush out whats there.
Cranberry juice is great for bladder issues too so drink lots of it (even if you dont like it, try to water it down).
If its still going on please get a docs opinion as sometimes you may have other problems like passing a stone (yes I know they are usually really painfull but I know people who have passed really tiny ones that have caused similar symptoms to yours).
Apparently stones are yet another issue that people with Crohn's are likely to get so dont ignore this.