Hi DarkJojo,
Thank you for your updates. So you have a Brooklyn Bedding Best Mattress Ever in the Medium and you’ve been sleeping on it for a week on the floor (meaning the mattress is directly upon the floor with nothing underneath it).
As you’ve only had the mattress for a week on a “proper” flat surface that won’t impact the feel and cause it to give more than it should (which could exacerbate any back issues/pains that you may have), I would recommend that you try and test it out in this configuration for a few more weeks. The time you spent previously with the Casper mattress and the BME with the box spring and/or old mattress underneath them can’t be used as a reliable indicator of performance or comfort, as those underlying surfaces weren’t appropriate and wouldn’t have allowed you to gain a good analysis of how the products performed.
If you could, I would suggest sleeping upon the mattress for a few more weeks in this manner and see if you become more comfortable. You may have a bit of “learned alignment” for your older sleep system, which can take a few weeks to adjust when your body is presented with a product that provides the chance for a better or more neutral alignment.
There is some information about the many different symptoms/pains that people may experience on a mattress and some of the most common causes behind them in post #2 here that may be helpful, but as you’re only one week into using the mattress on the floor I wouldn’t think that you’ve had a long enough time to truly acquire a good analysis to evaluate your current mattress, or have come up with enough good details to help point you in a new direction.
Hopefully you can use the mattress on the floor for a few more weeks and see if things get better for you, or if not then make a decision to move on to something else, but at least be armed with some better information to help you choose again.
Phoenix