Sorry you’re feeling this way. I’ve been there, and the best thing I did was to read. I even went back to evening college to get something more back in my life. Having a focus got me out of my head. Insomnia has stayed, but the anxiety and intrusive thoughts has reduced massively.
stay strong and in the meantime, the other suggestions here are great - write down your feelings, maybe even do some painting. Get off YouTube and social media if you can, or at least work towards it.
also go for walks more. It’s amazing how this helps with sleep and anxiety.
well being is so important, so have a think about things you like doing and make time for it. Swimming, yoga, listening to music, charity work, cooking, painting (try free pouring art, it’s ridiculously satisfying). It all helps, and although your brain is tired, your body might not be and that will make sleep more difficult.
sending you big hugs as I know it’s not easy. Don’t forget that the Samaritans are there for you if you ever need to just have a chat.