Worn out after 2 years. Back Pain.

We bought the Rhapsody Luxe Cali King 6 years ago for about 3800 including yhe Temputpedic Foundation. At first it was ok, except for the smell and the fact that it is quite warm. We knew this going in so I wont complain about it except that it is actually quite hot in summer. After 3 years it got really soft in the areas where most body weight is supported. We turned it every 6 months which by the way is a back breaking job in itself. 4 years in I could not sleep through the night anymore as I have to turn every 2-3 hours because it is so soft like sleeping in a hammock. I am not exaggerating. I got serious lower back pain- never had this before. Physioyherapist showed me exercises but every morning I feel horrible. At first I was in denial due to the fact that I spent so much money but after 5 years it got obvious and I cant deny it anymore. The mattress is complete mush where our hips and shoulders rest. To turn you literally have to dig yourself out. The problem is that Tempurpedics warranty makes you measure depth of impressions. That does not take into account the softness. Point in case: I can push with my hand easy 8 inches down in center where my hip rests. In other areas I push down 1 inch with the same force. 6 years in I try the warranty process again. They make you jump through hoops but I did it all, many pictures, proof of purchase, measurements, hours on the phone. It got approved and I will get a replacement- they say.