I hate my mattress. Ex wife picked it out. I sink in it and hate it. When we first got it, it felt firm. Is there a good firm mattress out there that does not sink in after a couple years. I like some flex, but this one sinks bad if I push down on it. I can get a rock hard one and a topper if need be. My back aches when I get up. I sleep on my side, back, and stomach (toss around alot). I don't want to break the bank either. Thanks.