Reoccuring Anxiety in Teens

Hi everybody. I am a 17 year female that has been diagnosed with an inflamed bladder or possibly, IC. The reason I am here is because this problem causes me to be extremely anxious. Prior to my diagnosis, I was constantly wondering what was wrong with me and whatnot. I did not want to go anywhere or do anything because I was so worried I'd experience an uncomfortable situation. I even missed my band concert, which is something that I used to love, but now just scared.
What I am here for is that I have a band concert coming up in a few weeks, and I am ALREADY fretting about it. I don't particularly want to miss another one, due to the fact that I feel silly, but when I am so anxious and worked up, I get so nervous and my stress goes right to my bladder. I'm not sure what to do & kind of ashamed to talk about it with my parents and band instructor because I feel silly.
I hate this whole bladder/anxiety issue because it has created a person who I am not. I'm just extremely frustrated at the moment and looking for some sincere advice. Thanks.