Hey @Lonelyboy17 , I'm sorry to hear that you're feeling so anxious about what happened, and worried that the post will be there forever. We have some good resources about cyberbullying here, - unfortunately it's something a lot of people go through.
The article I linked to has a few people who've been through similar things sharing what helped them - one self-care idea can be taking a break from social media, and taking a few days to focus on other things that bring you pleasure - maybe spending time in nature, or watching movies, or whatever you can do that's just for you. As @WheresMySquishy suggested above you can also report to the eSafety commissioner (there's a link in the article I put there too) - or I also know some people who decide to face it head on, and call out the person who's bullying them.
Anxiety in general can be really unpleasant and distressing, but there's a lot of things you can do to help calm yourself down. Exercise, meditation, and mindfulness are all things that can be really helpful to reduce anxiety - there's also some great apps like ReachOut Breathe and self help for anxiety management .
Hope you're feeling a bit better today.