Josie,
I'm sorry to hear about this sudden spike in your pain. You sound about as desperate as I was a little over a year ago when I blew out a disk at L5-S1. I'm not sure exactly how it happened though there had been an annular tear there already. I was shopping and started noticing a worsening of my usual lumbar ache. So I got the last few items I needed, got in the car and headed home. I was about half way home when my back started feeling like it was on fire and someone was stabbing me in the butt with a knife. By the time I got home I couldn't even stand. I crawled into the house on my hands and knees... I still wonder if anyone saw me?!
Yes, the pain is excruciating. I was already using Duragesic patches with oxycodone for breakthrough pain (for other conditions.) Still the pain was overwhelming. I would have gone to the ER if it weren't for my fear that they probably wouldn't be able to do any better of a job handling my pain than what I could do at home. Looking back on it now, I think I should have gone to the ER. They would have kept me, I'm sure. I couldn't stand or walk. I had to crawl back and forth to the toilet. I found tiny bits of relief in a hot tub, laying on my side (we have a large, garden tub.) And I caught a few minutes of sleep here and there by laying on the floor on my back with my legs up on a chair (bent knees, like in a sitting position.)
You have every right to seek out treatment at the ER. This type of pain is a very legitimate reason to go in. While this does sound like a lumbar back problem, I'm sure that you must still have cancer worries in the back of your mind. That fear isn't helping matters either.
Good luck and let us know what you decide to do.
--Kaylbe