PLEASE I NEED ADVICE!!!😭😭😭

My son is coming up 11 months, for the last few weeks, every time I put him down to nap or sleep, he screams his head off, like hysterically. It's an hour past his bedtime and he's still screaming hysterically, he's driving me insane. I have no idea what to do, he won't settle when I go see him at all. Please I need advice, this is all new. He's never done this before he used to go down no problem😩