Major anxiety

My boy was born December 18, he’s almost 9 weeks already. I was wondering if anyone else is having major anxiety. I had it right after he was born, like most new moms I’m sure. It got better as the weeks passed, but all of a sudden it’s returned with a vengeance. I’ll just have random thoughts pop in my head about him not breathing or dying or his older brother accidentally hurting him. I always check on him when he’s sleeping, but now it’s like I can’t sleep because I’m so scared he isn’t breathing. This isn’t PPD is it? I just don’t understand where all this anxiety came from 😞.