Phoenix:
Hi DarkJojo,
While I can’t tell what is causing you to sleep uncomfortably, you’re certainly not doing yourself any favours with your current set up. Using a 30+ year foundation (which is more than likely an inappropriate torsion system as I mentioned in my previous reply) is the first thing you should eliminate. Placing a mattress on top of that, and then placing your new mattress on top of both of these items, is creating an even more inappropriate surface for your mattress which virtually guarantees that your mattress will sag almost immediately.
You need to place your mattress upon a firm non-flexing (or very minimal flexing) surface, per Brooklyn Bedding. Use the guidelines in the foundation thread here as well if you need more guidance.
You would be much better served by placing your mattress directly upon the floor, as this would be preferable and more appropriate than your current setup.
Phoenix
Do you think my back pains could possibly stem from this poor set up? I know that when I sleep directly on the mattress below it’s sheer agony. I have springs poking up in places.