I'm really sorry to hear you're feeling this way. My recommendation is to try a different medium for a little while. Try something you aren't experienced with! It's a good way to still get your creativity flowing, while not engaging in the kind of art thats triggering anxiety. Sometimes taking a little break is necessary.
Though if it's really so bad that you're having anxiety attacks, you should talk to a professional- there's probably someone available at your school? I know making comics is part of your school curriculum, so taking a break might not be an option. There's really no way but through, so do your best, but take care of your mental health. Talk to a professional, or talk to a teacher. Take breaks. Brainstorm alternative ways to make things.