There really are three criteria for diagnosing Crohn's and ulcerative colitis. First is symptoms -- GI problems that include D, cramps, gas, possibly blood, etc., waxing and waning over time. Second is visual examination of the colon via scope and maybe the small bowel by camera pill and SBFT on X-ray. Skip areas of inflammation and possible ulceration point to Crohn's. while continuous inflammation indicates UC. Finally is biopsy -- but they are not always indicattive. A biopsy that shows inflammation deep into the bowel wall says CD; more superfocial inflammation generally means UC. In addition, there are complications (strictures, fistlulas, anal tags) that all point to CD. Finally there are some sophisticated blood tests (Prometheus test among them) that can also say with high certainty that you have CD. However, all these need to come together to really mail down a firm diagnosis. It's not uncommon for some patients to present with a history that says CD and/or UC and wind up being diagnised with one or the other or neither, maybe just irritable bowel, or celiac disease, or even a parasitic or infectious agent. The problem is that a half-dozen things can cause the classic Crohn's style symptoms (even gall bladder disease) and it takes some time in siome cases to really nail the diagnosis. The good news is that many of the medications prescribed for CD also help UC, and that over time as you respond (or not) to one or another med, the diagnosis becomes easier. There's a reason CD and UC are lumped under an umbrella of inflammatory bowel disease . . . they are so similar in many ways. That's why prednisone works for both -- it is an anti-inflammatory.
Give it some time and see how you respond to the meds and I suspect you will get a firm answer.