I don't think it's always possible to tell exactly which it is at first diagnosis. sometimes it is, sometimes it's not. I was originally dx UC. The first flex sig showed continuous inflammation, no skip areas and only surface ulceration. My biopsies continue even now to come back UC.
As time went by, the pattern changed. I developed a fissure, then
skin tags. The next colonoscopy showed skip areas and deeper ulcers. I was labeled as indeterminate for a while. Eventually I had my first fistula. Clearly now it's Crohn's, regardless of what the biopsy shows.
So, if you want a second opinion, you should definitely go after one! That is our right as patients. If your treatment is working, I wouldn't try to change it. (Though I don't consider adding probiotics a change in treatment. They are worth adding!!! I agree...) It is very, very frustrating to go back and forth between diagnoses. Personally I felt like a ping pong ball. In hindsight it only mattered because many of the treatments are approved first for Crohn's then studies follow for UC. (At least, that was my perspective.)
My first symptoms were bleeding and mucous with bowel movements. Urgency got worse as time went by, as did everything else.
Best of luck... Hang in there!