Thanks for your question. We are not aware of any Sealy Posturepedic mattresses made in the 2012 - 2014 timeframe that are two-sided. Of course, you can still flip it over, but what you'll find is that the bottom surface was never intended to be slept on. In general it will feel much firmer than the top of the mattress, and won't have the same cushioning depth and/or "memory" feel that drew you to that mattress originally. Of course, none of this precludes you from giving it a try.

For people interested in flipping a one-sided mattress, some people have even recommended purchasing a topper and using that to make the mattress more comfortable when sleeping on the bottom side. In your case though, the thing I am most focused on is that your complaint relates to back pain. This generally means that the mattress is not supporting your back in a neutral position during the night. Since you mentioned that you are experiencing this back pain after having the mattress for 3 years, I would assume that your mattress has given out (eg, sagging or "hammocking") and is no longer delivering adequate support. This type of back support issue is unlikely to be remedied by flipping the mattress, so my guess is that buying a topper to try to fix this mattress would be throwing good money after bad.

In terms of "washing the shell," we similarly are not aware of any Sealy Posturepedic mattresses made in that time frame that have removable, washable covers. So I don't think that will be an option for you either.

I hope that helps.