We're not giving our baby formula yet, he's getting expressed breast milk in a bottle while my wife is at work. We'll probably start supplementing with some formula in about a month or so if my wife is unable to keep up with expressing.
Our baby is nearly 3 months old, but usually only drinks between 3 to 3 1/2 ounces every 3 to 3 1/2 hours. Occasionally he'll drink 4 ounces, but that is very rare. Sometimes he'll only drink 1 1/2 ounces and then refuse to take any more. This is a bit worrying, especially as at this age it's my understanding that he should be taking 4 to 5 ounces per feed.
And sometimes when he's breastfeeding, he'll only be willing to feed for 5 minutes before he starts struggling and crying and refusing to suck, especially during early morning feeds. Night time breastfeeds are usually better and longer.
We are trying not to worry to much as he seems healthy and happy and it's impossible to make him eat anymore than he wants to anyway.
I guess he's just a light eater, just like his Mum. Definitely does not take after me in that department.
Graham