Hi tluna,
There are too many unknowns, variables, and personal preferences involved for anyone to be able to make specific suggestions about “which” mattress to buy or even seriously consider for someone else out of all the thousands that are available in the market based on specs (either yours or a mattress) or "theory at a distance (see mattress firmness/comfort levels in post #2 here) but the mattress shopping tutorial here has all the basic information, steps, and guidelines about “how” to make the best possible choices … and know how and why to avoid the worst ones.
Post #3 here and the posts it links to also has more information about choosing a mattress that would be helpful for those with larger body types or who are in higher weight ranges.
Once you reach step 3 in the tutorial if you let me know your city or zip code I’d also be happy to let you know some of the better options or possibilities I’m aware of in your area.
Phoenix