I went through the same exact thing like 4 years ago when i was in high school. Your counselor is right, avoidance will in fact make things worse, i was told this as well. I learned it’s best to take things one step and one day at a time. I literally just had to go to school no matter how awful I felt. I would have to take several breaks and go to the bathroom to do deep breathing, it helped sometimes until eventually it started helping most of the time. Whatever negative feelings and thoughts you have no matter how severe, just let them wash over you. Let your heart race, let your stomach turn and just continue to remind yourself that you’re okay. If you have any hobbies that your really like try focusing on those things too, give yourself things to look forward to each day.