Tips on getting baby to sleep at night?

FTM here! Week one baby boy slept four hours through the night (in a rock and play) then I started to get stressed about his neck constricting his airway, so now he sleeps flat on his back, but he will only sleep for 2 hours at a time at night...and alllllll day! Any tips on how to get a 2 week old to sleep at night and not all day?

Much thanks!!!!