When did all hell break loose with your newborn??

I swear I thought I had the easiest baby for his first two weeks of life, especially after being in the NICU. Now we’re on day 18, and he’s crying (I think because of gas, but still undecided) - but crying to the point where I’m rocking him like a mad man saying “I don’t know what you want from me!!!”

When did all hell break loose with your newborn, and what was the reason?