How to stay sane

My 3 week old has been fighting sleep the past week. I laid her in the snoo around 8:30 and she was doing good until 30 min later when she woke up crying. Now it’s 11 and we still can’t get her to sleep. My back has been bad since delivery and of course the only rocking she likes is if I’m standing up. It’s killing me, I’m frustrated because she won’t keep her eyes closed and screams if I’m not moving her.... I’m understanding now why they tell you to set them some place safe and walk away if you really have to... how do I get through this?