A couple days ago, my lower right back started hurting. It has gotten progressively worse over the past three days despite not running. I've had muscle strains in the past in my lower and upper back, but this feels different. When I've had muscle strains in the past, it has hurt to lift things, twist my back or run. This hurts sitting and even lying down. The pain is right where the top of my sacrum meets my pelvis bone....maybe a little above. Walking/ impact doesn't seem to bother my back immediately, but I notice as soon as I stop walking/ impact, it gets worse as soon as I am sedentary again.
I went to the doctor today basically to rule out a kidney issue as I have a nursing friend who made me nervous that pain in that area could be kidney related. My doctor wasn't worried about my kidneys at all as I have no other symptoms. She ordered an X ray and said the alignment looked normal. She told me that I likely strained a muscle. She said if it continues to bother me over the next few days, it could be bone or nerve related.
I'm just very confused as this feels very different from muscle strains I've had in the past. At times, it is very uncomfortable to just sit, stand or even lie down. My doctor mentioned the possibility of a sacral stress fracture, but I didn't feel the back pain on the last run I completed last Wednesday, and it doesn't feel worse walking than when stationary. I'm not having leg pain, so nerve pain isn't fitting either. However, I've never had a muscle strain that hurt at rest but not with movement. Has anyone else experienced anything similar or have any insight?