Reduction in milk supply need never be permanent. It's pretty normal to feed every 2 hours or so - esp in the evening. Being sick doesn't usually reduce supply in itself, but a couple of things can happen - because you feel so lousy you don't feel like feeding often so you feed less. Also because you are stressing you analyse the situation in minute detail. A few days of rest (to make you feel better) and frequent feeding will bring your supply back. You don't need to give anything other than breastmilk, and breastmilk protects against gastro in the baby. Hope you are feeling better soon