How do I stop the nervous poops?

I was diagnosed with generalized anxiety disorder. I am in college and my nerves and anxiety always go crazy the first week of school. I have class tomorrow, and I am super worried because when my nerves act up, I get gassy mixed with the feeling of having diahrrea while being constipated. I have irritable bowel syndrome, so I am constipated most of the time. I have taken laxatives. They help alittle, but none I have tried (enema, miralax, and milk of magnesia) clear me all the way out making it worse. Last semester, I had to run out of class to the bathroom. It was so embarrassing because I felt like I was about to have diahrrea, but I couldn't even go because I was constipated due to my irritable bowel syndrome, so I sat in the bathroom with the worse stomach cramps. Is there any remedies for this? I don't want this to happen again, especially on the first day of class.