Hump in the Middle

For a reference I'm 5'9" and 185 lbs., my husband is 5'7" and 180 lbs. My old hybrid mattress (Englander 21st Century Sleep System) was like sleeping on a cloud, soft on top and supportive underneath. Unfortunately, Englander no longer makes this mattress. This is what I was looking for in a new mattress. I paid approximate $2400 for this mattress and box springs and it is only 3 years old and at the end of its' life-cycle. I removed the box springs and put it directly on out slat platform bed, added a 3 inch latex topper for the last year, and it is still uncomfortable. There is a large hump in the middle of the bed and body impressions on each side where we sleep. Never felt like the mattress did in the store. So disappointed that a mattress costing this much money is so poorly made. My old mattress mentioned above lasted approximately 15 years. The local mattress store (not a big name mattress store) I bought this from no longer carries this line of mattresses, due to the complaints about the mattress. Enough said, buyer beware.