lets look at the average person
24 hours in a day
6-8 hours in bed
1 hour getting ready (shower, hair, breakfast)
2 hours commute (morning and evening) - probably driving or sitting
8 hours at work (most of it sitting down)
1 hour cooking/eating
18 - 20 hours limited activity across the day (including sleep)
4 - 6 hours spare a day
20 - 30 spare a week (mon - fri)
What are you choosing to do in those 4-6 hours every day or 20 - 30 hours in the week
Even if you did 30 mins a night of physical activity you are still only doing 2.5 hours of physical activity a week
30 hours sedentary vs 2.5 hours active
Do you still think your pillow or mattress is the reason you are in pain or stiff?
Stiffness is only one part of back pain but forcing your head, neck, hips, shoulders into one position when you are sleeping could be more detrimental.
Could you be more active - not just going to the gym -
Wouldn't you like the ability to support your own body and not depend on a pillow???