Hi Miss UK,
I think i am having a similar experiene. Lately either after or before my period, i seem to get a discharge out of the blue. It starts off as just a light discharge and is a brown colour - like old blood (like you get at the end of a period) but then all of a sudden it changes to bright red blood and it gets much heavier like i am in the middle of a period. That usually lasts a day - maybe 2. Then it goes bak to small amounts of browny red discharge again. Plus i am still having a normal period every month as well. It's been going on for over a month now and i know i should ask my doctor about it but i am so scared. And i don't want to find out that i have another problem on top of the crohns. It's funny because i had a smear test a month ago (when i was diagnosed with a hiatus hernia) and they told me it was normal. So i am totally confused with this, not to mention worried!
Does this sound anything like what you are experiencing?