Hi Yowe & welcome. I'm pretty new here too
First things first, as far as I am aware UC is fairly easy to diagnose following a colonoscopy and the analysis of biopsies so if you can push for such investigations then you may have your answer. IBS is quite distinct from the IBD spectrum which includes UC and Crohn's. I know that my GI noted only areas of 'inflammation' during my colonoscopy but the histopathology report came back with a firm diagnosis following analysis of the biopsies - moderately active UC. Stress can be a trigger for IBS and that being the case IBS can be managed more easily than UC as it tends to be episodic. Not pleasant of course, but fortunately less in need of heavy duty meds so if you have IBS be grateful! You can probably manage your symptoms via a combination of relaxation therapy and diet but if it's UC then these measures alone will not deal with the issue.
As far as Essiac is concerned, it's great that you feel so well having started to use it but it hasn't exactly had a good press has it? I think it probably has a lot of reputational repair work to do as a result of (apparently) marketing itself as a cure for cancer:
en.wikipedia.org/wiki/Essiac Depending upon the combination of herbs it contains it may have a relaxative effect in which case that of itself may assist with alleviating stress.
I hope you get your answer soon - knowing your enemy is the first step towards winning the battle.