PLEASE HELP- 18 DAY OLD BABY WON'T STOP EATING

I am going insane. I pump, I breastfeed, and I even give formula at night on top of my breastmilk and my 18 day old baby won't stop eating. I wake him up every 2-3 hours to eat and he was taking 2-3oz last week per feeding and now he wants at least 4oz, today I had to give him 5oz. I gave him 4 oz when I woke him up and he wouldn't stop crying. I changed him, burped him, tried comforting him, gave him a pacifier, I spent another hour trying anything and everything I could think of but he kept crying looking for boob so I pumped and gave him 1 more ounce. Now he's still not sleeping and a little grumpy making pushing/pooping noises but at least not crying (hasn't pooped though). I am going insane. Please don't misunderstand I love this little nugget more than anything but I feel so desperate and frustrated. I don't understand why he eats so much my breast have more than enough milk yet he always wants more. He spits up sometimes after he gets stuffed but if I don't give him more milk he won't stop crying. Anyone else have this problem? He has no issues with weight or poop/pee (3-4 poops per day and over 8 pee) I'm wondering if it's his belly. Our next appointment with his pediatric doctor isn't until April 7th. Someone please help me out this is my first baby and I'm so lost. ❤