Mommy's with small children can't get good sleep because of a restless…

Mommy's with small children can't get good sleep because of a restless baby. And I have it the other way around. The child is sleeping soundly, but I can't. It seems like I want to sleep, but I can't fall asleep... Already the third day, I sleep for 3-4 hours a day... Such insomnia has happened twice in a month. What is this? I have three kids, without a kindergarten, without a nanny. The little one is half a month old. Is it from exhaustion? But before it wasn't like that.