What is Ruminating?

I'm having the hardest time right now with my own ruminating negative thoughts that may or may not possibly come true. I fear the worst and replay what that looks like in my head over and over. The best I can do is my best and wait for the horror to end. I want to cry, but can't. I'm scared and alone in my head. My anxiety is extreme. What should I do in the meantime while I'm going through this? How can I minimize or stop the way I'm feeling? Please, I need help.

Advice needed please: Has anybody ever been in a situation where something traumatic or heartbreaking was happening in their life and struggled with rumination? I know there is like a normal amount that you should process something and cry it out but I don’t know that it is conducive to anything to do that on and off for hours? Wouldn’t it at a certain point be considered unhelpful rumination? And if so how does one stop? Because I’m going through something so hurtful and confusing that I don’t know how to stop thinking about it and the usual distractions don’t work for very long. And idk how important this is but it just happened today so it’s very fresh which makes it even harder to not think about and “figure out” why x, y, z happened. Goodness, I’m sorry if I’m weird or a baby

Two things are happening: I get thoughts that just keep looping. They almost feel like song stuck in my head. Also, I’ll imagine something and I feel my stomach drop. Then as the seconds go by I keep getting fragments of the this thought but with different details. For example, it’s kinda like how a “vision” is portrayed. I’ll get a glimpse of the thought and then it’ll rapidly expand into something worse every few seconds. I don’t know if I’m causing this or if it’s just an automatic thing like any other intrusive thought. It feels unavoidable, idk if this is a compulsion or if it’s just another manifestation of an intrusive thought. Apart from that remembering an intrusive thought triggers the full thought again and then it just keeps looping or expanding. I don’t know how to stop any of this. Help?