When a person takes 3 wrong antibiotics for something viral &it wipes out all good gut flora and they are very very sick months later, what do they do?

Find out why you are: very sick. Although it makes no sense to take 3 wrong antibiotics for a viral infeciton... it also makes no sense to assume that your present illness is do to "wiping out all good gut flora". Tell a doctor your symptoms and your concerns about the antibiotics and have him find out what is making you sick at this point. You can eat yogurt or take pro-biotics if you are worried about your flora.