I agree with Caseman 100%, Erica.
You mention your school band so I assume you are a student. I had my first panic attack while in high school. One of the ways I earned money in high school was performing magic, and at one venue the crowd was huge with a full orchestra and this was beyond what I had ever experienced or expected. I freaked, but somehow got through the performance, breathing heavily, shaking and obviously appearing nervous to the audience. The next scheduled performance my anxiety level was raised not because I was afraid of performing, which I loved, but because I was afraid I might panic or appear panicky. This is a nasty spiral, as Caseman says and I strongly suggest you intervene now. Somehow I got through high school productions, college presentations and law school moot court all without medication, although I experienced anxiety on the verge of panic every time. This is not a good way to go through life. It was not until I was a practicing attorney that I realized my performance affected the lives of my clients and decided to talk to a doctor about medication.
An understanding doctor will offer both Xanax and propranolol. In my experience, Xanax at .25mg does nothing, but .5mg makes me drowsy so I prefer not to use it. Propranolol at 20mg takes the edge off by reducing the racing heart and high blood pressure of the fight or flight response. I've taken up to 40mg propranolol. I take both medications, only as needed, depending upon the circumstances. There are even times I don't feel I need the medication, but it is comforting to know it is there, just in case.
Please talk to your doctor. Some are reluctant to prescribe drugs for performance anxiety, but that is only because they have never experienced a panic attack themselves. In that case, find another doctor.
Get some help now to minimize the effect of performance anxiety on your life. You can lead a full and satisfying life with performance anxiety, but medication can help. Even talking to someone helps.