Newborn feeding trouble. HELP!!

Sarah
My baby is 5 days old, yesterday they checked his weight and he had dropped one pound (more than the normal 10%). I was freaking out, but the nurse suggested a strict diet of 2 hours on breast and topping him off with an oz of formula. We did it and checked his weight and he had gained back his pound. Well we got back from the dr visit and he hasn't eaten for four hours, we gave him formula and he threw up and after I pumped and he only took about an oz. he's been sleeping. I am worried, I don't know what to do! Anybody go through this or have any advice? Please? FTM and I am freaking out