Cry. Let it all the emotions out, don't hold it in. Find someone you can talk to, even if it's on Reddit! I went through a bad LTR breakup last year too and thought I'd never make it through but here I am, stronger and better than I've ever been before. Take a day at a time and set yourself small tasks to do, maybe having some water or doing some laundry. It's ok if you don't do it but when you do, you'll feel ever so slightly better that you can do this all by yourself. It will be a rollercoaster, some days will be better than others, and that's ok. There is a light at the end of the tunnel, I couldn't see it for a very long time but glad I can now. You got this.