Hi Imercadante,
The first place I would start your mattress research is the tutorial post here which has all the basic information, steps, and guidelines that can help you with how to make the best possible choices … and know how and why to avoid the worst ones.
This is most likely an indication that the mattress is too soft for your particular body type and sleeping positions. If you purchased a mattress that was “on the edge” of being too soft when it was new (after the break in period) then even a relatively small amount of foam softening which would be normal with any material can put you “over the edge” where the mattress may no longer be a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). There is more about this in post #2 here. It’s also possible that your mattress uses lower density memory foam than would be suitable for your body type if you are in a higher weight range (see the guidelines here) because 4 lb memory foam will soften more rapidly under the heavier parts of the body than 5 lb or higher memory foam. There are also some suggestions in post #4 here that may be helpful if your mattress is too soft or has developed soft spots but in most cases there aren’t any simple ways to “fix” a mattress that has developed soft spots (or was too soft in the first place) that will provide more than a temporary or partial solution.
There is really no such thing as a specific type of mattress that is “good for backs” in general because each person’s body type and sleeping positions and their physiology or heath issues can be very different and a mattress that is good for one person’s back may make another person’s back issues worse. It really depends on the specific design of the mattress and how suitable it is for you in terms of PPP and this has more to do with the specific design of a mattress and how well it “matches” your specific needs and preferences than it does with the materials in the mattress (see mattress firmness/comfort levels in post #2 here)
You can see my comments about the Saatva mattresses in post #1 here and there is more feedback in the rest of the topic as well. A forum search on Saatva (you can just click the link) will also bring up more information and feedback about them as well.
The Saatva mattress uses a Bonnell coil in the support core which has more motion transfer than pocket coils (you can read more about the different types of innerspring in this article). The comfort layer uses a compressed pocket coil or microcoil so this would transfer less motion than other types of innersprings but other types of innersprings aren’t used in comfort layers so a comparison with other types of foam comfort layers would be more relevant and it can transfer more motion than than most foam materials … especially memory foam (which is the best at motion isolation) or latex.
Comfortaire was purchased by Select Comfort (Sleep Number) so they are the same company but their mattresses are different. You can read more of my thoughts about airbeds in general in this article.
You can also read some thoughts about the Natural Form mattresses in post #2 here.
You can read more about adjustable beds in post #3 here and the adjustable bed thread it links to but if you are a back sleeper then in many cases some slight elevation can help relieve pressure and help with pain in the lower back yes. A pillow under the knees can help as well.
If you do decide to buy an adjustable bed then I would confirm that any mattress you are considering is suitable for use on an adjustable bed. In most cases any foam mattress and most mattresses that have a pocket coil as a support core and that aren’t too thick (12" is a reasonable maximum guideline) so they can bend with the adjustable bed without damaging the mattress would work well but it’s always best to check with the manufacturer to make sure.
Once you reach step 3 in the tutorial and are ready to start testing mattresses then the better options or possibilities I’m aware of in the Columbus area are listed in post #2 here.
Phoenix