Baby is sleeping., I am not.

Whyyy can’t I sleep at night?? My son sleeps so well now and I am constantly awake. I can never fall asleep even if I’m actually tired. My brain plays a million scenarios in my head or then the baby makes a noise on the monitor and I think he’s waking up. It’s 2am and this is the 4th night in a row I’ve stayed up this long. Worst part is if I actually fall asleep I wake up in a couple hours and have to go check on the baby. Will it ever end?? I’m not gonna make it when I go back to work. 😩