When my 5 and half week old sleeps

My son is 5 and a half weeks old and he slept about 9 and a half hours. ( I had to wake him up when I finally woke up and realized how long he was sleeping ) I had also slept that much too. Felt so nice now I have more energy to do stuff today. He just ate his bottle and now hes sleeping again. For a 5 and a half week old baby he acts like a 3 month old and almost as big as a 3 month old lol. ( pictures of him wanting to stand and holding his head up real good )