how are you supposed to sit with all that pain, confusion, and regret and just do nothing?

I care about someone alot, and they're mad at me, or gone, or hating me. My brain starts spinning constantly, replaying everything I did wrong, everything I should have said or shouldn't have done. And that ache in my chest. It's so heavy that just sitting there feels like it's going to swallow me whole.

I start thinking:
— What if I don’t say something and they forget me?
— What if they want sorries and me not saying anything is bad?
— What if we can go fix it and it doesnt have to end like this?
— What if they think I never cared?

All that what ifs just drives me crazy. I've been a horrible person cause i just had some bf i hurt so much of my friends. I want to apologize but i don't think they'd want one from me not specially after everything.