Yes, absolutely tests can miss things or be "normal" or inconclusive even when something like IBD is going on. I have presumed IBD as well but I'm also not fully diagnosed in spite of having had many tests. My test results are always frustratingly normal, sometimes IBD just hides really well and bloodwork isn't always 100% reliable (for example, I've read that CRP & ESR - inflammatory markers in the blood - can be normal in about 10% of the IBD population, even during a bad flare - my CRP & ESR are always low/normal so I presume I'm in that 10%). For Crohn's specifically, it can manifest anywhere in the digestive tract, literally anywhere from mouth to anus - in other words, that's a lot of digestive tract that they have to check, and it's not easy to see (or particularly to biopsy) the small intestine. And something like microscopic colitis is just that, it's microscopic - meaning when they do a colonoscopy, everything will look totally normal. They can only find it on biopsy. Also, with both Crohn's and microscopic colitis, they have "skip patterns" meaning the inflammation is patchy and they basically have to biopsy the right spot to find it, particularly with microscopic colitis. So, when you have your scope, make sure they know to take lots of biopsies! Good luck with the scope, I hope you can get some answers soon. Hang in there!