Why the IKEA latex mattress become soft?

Both I and my wife sleep on twin size IKEA latex mattress, mine become very soft that I feel back pain after sleep but my wife’s doing OK. I can sleep on her mattress without problem, why?

Hi zzeng7712,

Which Ikea mattresses do you own?

Is there a significant weight difference between you?

What are you using for the support system under your mattress?

Phoenix