Like sleeping in a fluffy hole

We were told this mattress was fine for someone 300 pounds. We didn't realize the place we bought it from had a zero return policy. I was rapidly losing weight. At that point, I was maybe 305 pounds? Boy, that cutoff must be *exactly* 300 pounds because the mattress almost immediately collapsed under my weight. Also, they sold us an adjustable base and this mattress is only comfortable with the proper box springs but we couldn't afford them at that point. We saved for months for this purchase. Now it's 2 years later, I'm 100 pounds lighter but I still wake up crying from the pain. And the sides look like a wave. One side is arched like \ and the other side is arched like \ so when you sit it practically touches the base of the bed on the side where it is permanently about 3 inches adrift from where it should be but curling under my knees. If I sit on the other side where the 3 inches hang over the bed I feel. like I'm going to fall off. It looks like a permanent wave caught still. The worst part, though, is where I guess the coils shift? Because when I lay down I feel like I'm laying on a normal bed. Then when I wake up 2 hours later, I'm pushing myself out of a hole my torso has fallen into. Do NOT buy this mattress. Seriously. I think I'll buy the harmony lux next because I can't afford a 4" purple.