I've had pain in my abdomen since my csection of twins. no hernia detected. laying down and pressing on belly button there is a huge hole in abdomen?

Could be a hernia : This depends on what you mean by huge hole. Some people will have a hernia at the belly button called an umbilical hernia that can be repaired as a simple surgical procedure. Others have a separation of the muscles called a diastasis. This can also be fixed surgically but is cosmetic in nature. This diastasis is not isolated to the belly button.