Is there a multivitamin to take to make you hungry ? or eat more. haven't been eating due to stress and thinking blood in stool and bad headaches

No: Multivitamins don't do that in the U.S. But, if a person takes the kids' gummy vitamins, he can chew 4-6 of them each day to add up to an adult dose. Because they taste like candy, they are likely to make him want more candy, Gummy Bears, chocolate, or snack foods. This is not a nutritious way to do things, but is likely the only way any multivitamin can make a person want to eat something else