There are varying symptoms that can occur with flares, and they can differ from flare to flare as well...if your stools still aren't formed and you're still having issues with frequency then regardless of blood or not, that sounds like a flare...and of course people can have both IBD and IBS at the same time, they are 2 separate entities with similar symptoms. Based on what you've described is sounds like an IBD (your colitis) is flaring.
I do find it odd that your doc would assume you are dealing with IBS based on what you've described your symptoms are....did he scope you recently and not find any inflammation and conclude that you are experiencing IBS?
Any good GI would know that bleeding (unless due to hemmies) is not a symptom of IBS but rather IBD.