LOL, good for Gorka!
I used to have a lot of back pain. For 22.5 years I had progressively worse back pain due to a ruptured disk. I had horrible medical advice and very little relief.
But, then in 2013, as I was actively praying for guidance in finding a doc who might be able to help, I was led to this book: Healing Back Pain by John E Sarno. It is a quick read. Available on Amazon. I use a kindle version.
I don't think it is very well written and, imo, the advice it contains is encapsulated on one page. But, when I applied those psychological principles and began acting on them, my back pain left immediately. It was as if God said to me, "Take up your bed and walk."
I put this out there just in case someone else has back pain and wants to try it. No doctors, just psychology. And God.