My two-pence worth, having suffered. I'd gone through my 20s and 30s always having back pain at the beginning of spring, when the first digging of the garden started. At age 31 I was tested for disc problems and fitted with a ghastly corset "for life". Well, I used to put it on when the pain was bad, and it felt better an hour later just to take it off!. At 44 I finally did some serious damage in the gym, and went off sick. The CAA rule by the way (unless it has changed) is that if you are sick longer than 28 days they will temporarily suspend your medical certificate. My consultant did all the usual tests and found a prolapsed L4/5 disc. He took the offending bit out and it worked a miracle cure. I was off for a few weeks because I couldn't fully straighten my leg (scar tissue?), but was soon back flying again. Now, over twenty years later, I'm happily retired and running half marathons, with no sign of any back pain. Two points: see a specialist and take his advice, and don't worry about the CAA Medical Branch; they're keen to get you flying again. Good luck.