I have always had lower back sensitivity from lifting poorly or bad posture, however I always recovered quickly. My new "memory foam" mattress was touted to help sensitive backs.. mine was fine.. for the first few months.. then, very slowly, and ever so subtly, my back got progressively worse to the point I could not stand or sit without major pain in lower back. I went to chiropractors, and Kaiser PT for weeks, exercised, with no relief. I just never suspected my $4000 bed was destroying my back !!!!
Finally, I tried sleeping on the floor one night... and I felt better in the morning. After 3 nights on the floor my pain is almost gone and I am feeling much better. IT IS THE BED, and it was INSIDIOUS how gradually it affected me.. Be warned.