Is there really a afterlife?

Hello, I am terrified of dying and losing the ones I love. I know it is a part of life but I struggle to come to terms with the fact that they’re could be nothing waiting for me and my family..

Could what people experience with close calls with death just be the brain still working minutes after being pronounced dead? When you see a loved one after they pass, is it just your brain helping you with grief? Do I have to be spiritual to know there is something after we’re gone? I need comfort, thank you.