Help me please

I have a thing with my friends tomorrow that has been giving me so much anxiety. I don’t want to go at all!!! It’s a big group photo shoot. We are wearing clothes that are out of my comfort zone. And I really just want to bail on them. But at the same time would feel really bad if I did. But I’ve been worrying about this for a long time and I just don’t want to do it. What would you do?