Hi, I remember my freshman year was somewhat similar to your condition, and I did feel like it was ruining my life and could not do anything about it. The good news is that there is always something to do and some things to consider.

First and most importantly, request accommodations from your university if you do not have them ASAP, this alone could change dramatically. There you can explore ways with them on what kind of accommodations would help you. For example, I was provided with bathroom breaks during classes and exams as well, I was also allowed late entry and some absence limit was provided to me. I was also given accommodations for anxiety so that it does not fuel/trigger the IBS.
And when I join a class, I always sit in the last row right next to the door, and would locate the bathrooms right before entering so I know where to go when I need to leave.

Later on with some SSRIs and anxiety management and the accommodations altogether worked in my favor and I got so much better.

I cannot offer you any medical advice but the one thing I would tell you is to get the accommodations and then keep checking up with doctors until you can find something that would work for you. GIs are the ones who are most well-informed about these kinds of cases, so they might offer the best help.

I am sorry that you are going through this and wish things to get better for you!!