hot a formula fed 3 week old would generally drink 4 ounces (120ml) approx 5 times a day.
My 4 week old has just gone to 4kg and he should be on 5 ounces (150 ml) but will only drink around 4 ounces and goes approx 4 hours until his next one but if I give him breast milk he will go a lot less and seems less satisfied.
I agree with mogz it sounds like your lo is having a growth spurt and is catching up on some weight. Lleyton did the same about a week ago and was eating all the time.
I would feed him when he's hungry and he will settle when he's full and if it continues maybe talk to your hv about a hungry baby formula.
I still now have to give ds3 another couple ounces not long after his bottle as he's still not settled and once he's had enough, he sleeps.
I do make sure I try to wake him to finish his feed as I've found he sleeps longer and doesn't wake as much for more.
Good luck for tomorrow stom xx