Struggling with ruminating and feeling like I’m in danger

I have no idea how to stop ruminating or how to cope with it. I feel like nobody understands and it is so lonely.

The moment something bothers me, my brain plays it on a loop until I “solve” it. It tortures me.

For example: right now I am convinced my partner is cheating on me. And that my mom could be sick with something bad like cancer. Even though I am not in immediate danger, my body feels stuck on this. Like I feel hot and sweaty and anxious and I can’t stop thinking about it. Even though in this moment nothing bad is happening, my body is convinced there is.

Does anyone have advice for how to help this?