Overnight Changes

It seemed like overnight, my little baby has grown so much. Just holding him now, he is the length of my torso, he requires two arms, and my arms get tired quickly. He stands now when I hold his hands and when he's tired he goes in a standing position but then burries his head into my chest. He's playing with toys now on his jumperoo. He's sleeping in his big boy crib for 7-hour stretches now (night #5 he has done this). He's going into his crib for naps. His 3-6 month clothes are starting to get short (!!!). What happened to my little baby boy? I am excited to watch him continue to grow and learn new things, but I miss my little newborn.