Fine for a few years, now no support

This was an incredibly expensive bed when we bought it, and took years to pay off. It was fine for several years, and I loved how cozy it felt climbing in each night. I don't sleep hot, so I've never had issues with it being too warm over the years. Sadly, a few years ago I started having frequent low back pain, and it has gotten worse over time. I started to suspect that the mattress was to blame, because I had the most pain while trying to change positions at night, and could hardly move in the mornings. I began sleeping on an older inner-spring mattress we had in our guest room, and immediately confirmed that our iComfort Prodigy bed - such a splurge for us - was indeed to blame for my pain. We are heading out shopping for a new mattress today. I am frustrated that it may take years to find out if we made the right choice. I know I'm not spending that kind of money again. Very sad.