Princess Zoe, I went through something similar for 4 months last spring & summer -- severe pain in my left lower back. It hurt standing, even more sitting, somewhat less stretched out in bed.
My internist referred me to physical therapy but 6 weeks there gave little improvement. X-rays and a MRI showed some spinal deterioration consistent with aging. That was causing a pinched nerve which in turn created a muscle spasm ---> pain. Taking the recommended Ibuprofen and other Rx pain relief meds helped very little, if any.
I cancelled plans for my annual pilgrimage to a Vermont reunion to see family and friends.
Finally my physician referred me to a pain center. The MD there suggested I switch from ibuprofen to Naproxen sodium (Aleve is one brand, I used cheaper generics) and also fitted me with a portable electrical stim device (battery powered, the control unit is no larger than a deck of cards and can be worn on a belt, wires lead from it to stick-on electrodes near the painful spot) with an adjustable intensity of a rapid off-on slight shock that blocks the offending pain. (It doesn't take very long to find that preferred level of mildly unpleasant shock which cancels a far more unpleasant level of back pain.)
Both did wonders. The Naproxen was a great relief and what little pain was left over from that, the stim unit easily conquered. I wore the stim unit for about 10 days and took the N.s. for about a month.
Pain gone.
Several times since then I've used the N.s. as needed for a couple days.
The pain Dr. said some people respond quite well to the Ibuprofen while some much better to the Naproxen.
Later, a fellow choir member was complaining about
his lower back pain and he was somewhat bent over. I suggested the N.s.; he used it and got good relief and has several times since.
Causes of back pain very a great deal. Don't know if any of these experiences might apply to you but I pass it on in hopes it could be useful.
Best wishes for getting relief SOON!!