A back issue is amongst the most serious and recurring possible; my Mother underwent three separate back surgeries in attempts to ressurect her health; a simple vertebrae fusion, a spinal fusion and then a subsequent removal of the spinal fusion properties, because in each case there was no improvement. She was an extreme situation, obviously, as she was only 5'4", 110 pounds with little-to-no muscle. . .that said, I learned quite a bit about back maladies during this whole recovery process.
In short, an MRI, a CT Scan and XRays should be done (provided you have good insurance/coverage) because each will reveal different insights into what may be the source of your back pain.
The largest factor to remember is that your back is involved in EVERYTHING you do, from sitting to walking to standing. Lying down is the ONLY way to fully allow your back to recover, and each twist & turn will further agitate whatever it is that's bothering you.
The best thing you can do at this point - assuming the malady is not too serious - is stretch and strengthen your back on a daily basis, not to the point of pain, but to the point of exertion. That, supplemented by a sustainable diet and limitation of exertion should help you get back to a somewhat 'normal' level, and hopefully preclude any serious issues in the future.
PM me if you need more details, I dealt with my Mom's situation for about ten years from minor to major and have some additional insight/knowledge that may help.
Ev