Should I call labor and delivery?

I’m 23 weeks and 3 days pregnant. My uterus feels pretty hard right now and uncomfortable and my back is kiiiilllinggg me. I don’t feel like I’m having Braxton Hicks or actual contractions but I don’t know. This is my first pregnancy that’s gotten this far so I don’t really know what they even feel like.

My OB’s office doesn’t have an after hours line. All the OB’s in the office rotate being on call at the hospital so I either have to call L&D and speak to a nurse or call the hospital on call line and they page the doctor on call to call me.