Someone please help me get these depressing and scary thoughts out of my head?

I keep thinking about dying and out it WILL happen someday and I keep thinking that there really isn't anything after death: we all just cease to exist. I can't even fathom what it will be like, not existing forever. I just seems so obvious that that's how it will be. Please don't leave answers about how "we'll all be with God in heaven" because I can't make myself believe that and it's really not comforting. I am shaking badly and I can't stop crying. I'm really sad and panicky right now. Please someone just talk to me. I feel so alone right now, even though I know everyone dies. Please I want to stop feeling like this. If you have any tips to stop panic attacks please tell me, I'm really suffering and anything like breathing exercise or something will help.