Advise on feeding newborn??

So my newborn is now 2 weeks old, he is a great baby and is barely ever sick! Hes taking his milk brilliantly he is on 3 ounce every 2-3 hours (hes very greedy) the problem is he still seems to be starving after these feeds and I'm scared of overfeeding him! I try all the other alternatives to why hes gripey but its obvious its hunger with his mouth looking for food and him suckling his hands like a maniac! What can I do?? Do I put him on a hungry baby milk? Do I feed him more even tho it can make him sick? If I dont he will scream and scream! He doesnt poo everyday either and when he does manage it's as if hes struggling alot! Hes been maybe once in 3-4 days and with how much he eats I'm worried his belly will get sore when hes not passing the milk through 😭😭😭 I'm so beyond stressed and tired I feel like I'm doing everything wrong