My son is a week and 5 days and I started off with breastfeeding and switched to formula. As soon as I switched him to formula once or twice a day or sometimes not at all he will vomit (not spit up, vomit everything in his stomach). He started off on Emfamil newborn, so we switched him to Emfamil gentlease. He's been doing a lot better but still vomits. I feed him with him sitting up, I burp him every 1-2 oz he drinks. I keep him elevated after he eats. He still Vomits. I called his doctor and all they told me was to call back if it gets worse.