Mattress Type after trying an Eve mattress

We have a slatted double bed, I weigh 9 stone and partner 12.5 stone have previously had a Sealy Posturepedic which I never found particularly comfortable and it gradually decreased in comfort over the years until could take it no longer.

Have since tried several within a wide range and find that all are comfortable in the short term and after a few weeks become less so. Most recently we have tried the Eve mattress which we both found particularly bad. I wonder if you could make a recommendation.

Price is not an issue for comfort as am starting to believe it may be me that's the problem! Can you help us find the right mattress type?