SEALY POSTUREPEDIC MATTRESS LOST IT SHAPE IN LESS THAN A MONTH

I bought a Sealy Posturepedic Queen bed MK II with Aloe Vera mattress, 3 weeks back the mattress has lost its shape. I am weigh a104 kg. A request when we go to buy beds please specify the maximum weight a mattress can withhold without losing it shape. We cannot be buying beds every year. I am very disappointed by the quality of the mattress.