Mattress does not last

I got this mattress about 2 years ago. When I first got it it was great, now it's so crappy, I can feel the springs, and sometimes I hear like stuff is breaking inside. The mattress feels so lumpy now (when I first got it it had some firmness to it), now the surface is uneven. My husband and I are both thin people and I have been experiencing more and more back pain and difficulty sleeping. I also have to say it does not help regulate your body temperate, it gets hot and stays hot. It's like it will absorb heat and retain it which makes it difficult to sleep at times, even though we have the AC blasting. It feels like we are sleeping on a stove. I'm throwing it away and getting a new one from a different place. I have asked everybody I know and they tell me good mattresses last at least 5 years. I have only had this one for barely 2 years.