I'm so sorry you're struggling...
What usually helps me is distraction. Can you do something to distract? It would be best if you could be with people but if you can't try doing something physical-exercise, cleaning your home (watch YouTube videos about cleaning and declutterig-motivational and forces you to be active and focus on here and now). Go for a walk, go to the cinema or theatre (I've learned to go there alone and not feel awkward) Listen to music, watch something funny or relaxing, create art, read an easy book.
It's very difficult when you're overwhelmed by emotions and thoughts and you probably have no desire to do these things. But try to force yourself and you'll see you'll feel better.

What helps me with emotions is describing them physically. Where in your body are they located? Is your heart heavy? Is it in your stomach? What colour and texture is your anger? Red? Light? Smooth? Try describing the physical sensation in your body and just observe it. You may draw it if you want to. Just breathe into it.
Then find a spot in your body that feels secure, such as your feet touching the ground (or other part). Focus on that, how you are supported and stable in that part of your body. Then focus on your negative sensation and back to the safe part... Change your focus from one to another and see what happens. For me, negative emotion usually disappears.

If you can't stop ruminating try reciting something, name capital cities, chemical elements, list as many singers or authors as you can, if you speak a foreign language try to remember words related to "kitchen vocab"... Do this for 5-15 minutes, it should stop negative thoughts for a while.

Good luck!