Welcome to this board.
My little experience with going to the hospital is that once they know you are a "spiney" as we affectionately call ourselves here, they pretty much want to just give you something to ease your pain and send off and tell you to make an appointment with your spine surgeon.
I would think you might get a similar response, but dont let that dissuade you from going if you feel you have no where to turn and you might get lucky and they can try and help you further.
It does sound like either the injection has caused some atrophy of the muscle or that your spine surgeries have also been a contributing factor and that those muscles have gone inactive for a long period of time.
I have an indentation in my lower right lumbar wall, closest to my spine. That muscle shut down probably when I injured myself back in June 2003. I have been told by my rehab therapist that it is possible to get that muscle active again and it's just going to have to "relearn" and will take some work and time.
So what's happening with you may be the same and not permanent muscle loss.
I would guess all the issues you mentioned are contributing to your pain level and not just that muscle that is atrophied. Though that muscle does support your spine and without full support, your spine is vulerable to more issues. So it's certainly a factor.
The only thing I can suggest between now and your appointment is to stay on your meds and ask for something stronger if those are not helping you while you wait. And if you just can't take it.. go the ER.
We certainly understand your issues and your pain. Please continue to post here. You are in good company. All the best to you.