Just need some insight

Can someone please tell me what going through a miscarriage is like! I know the mental feeling my heart is broken completely I can’t think straight I’m mad sad and don’t understand why, but what about passing the baby. What helped you get through it? What was it like? I know everyone’s different but how painful was it? You don’t have to talk about it if it’s to painful for you but I was told today I’m more then likely going to start having my miscarriage I was suppose to be 12 weeks! And the thought is just so heartbreaking that I actually have to pass my dead precious baby!