Sliding off-no side support after 2 yrs

I am extremely disappointed in the quality of my "luxury mattress". A Chattam & Wells Grand Palace. I was sold on the websites claim for the high quality of manufacturing-being a craftsman myself it was important to me. I also was happy that it was made in America. The problem is the lack of support. We have small dogs that sleep in the middle of our bed, and we are banished to the sides. Unfortunately, we both feel like we are sliding off due to lack of support. As a result we wake up tired, and extremely sore as we feel like we are fighting to stay on the bed. And, the middle is now higher than the sides, so you are stuck in your "spot". I am not at all impressed considering it cost $3700 just for the mattress-for that I expected much better.