Sagging within 5 years and seems to have fiberglass shedding

This was my 1st mattress I bought myself and I originally went with one that was too firm a Beauty Rest Black. I was able to exchange it and pay the difference, and I wanted something comparable to an Aireloom without needing to pay so much. I went from one being too firm to what I thought was a comparable higher end like Aireloom and this mattress barely lasted 5 yrs. I purchased it 7/20/19, and even after I've rotated it, it's like sleeping in a hammock. I also have a sealed protector over it as well, and there's chunks of white fibers all over the top of the bed. I reached out to Sherwood, who claims there's no fiberglass, but there clearly is. I wasted a total of $1400, including tax and the cost of the box spring, and I'm buying a new mattress today. Do not waste your money or your time as I can barely walk each morning that I wake up. Rotating it did nothing and even though the opposite side that I sleep on was rarely used, it sags just as bad on both sections.