Lower back pain

Gwen • Had my sweet rainbow baby girl on April 3, 2017! 👶🏻🚼🍼 So incredibly blessed. ❤️
What are some causes for lower back pain? I have had it for about a week and a half now. It goes away when I take acetaminophen but once it wears off it comes right back. I'm not pregnant at the moment so I know it's not because of that.