Hi there -- Thanks for your question. First, I would make sure that you don't have your mattress upside down. The bottom side of most mattresses is not meant for sleeping on, and would feel much firmer than the top side.

If that isn't it, I would try putting your mattress on the floor for a night. If it feels soft like it used to, then you'll know that your new setup is doing something weird to make it feel firmer. Honestly I don't have a lot of ideas as to what that could be without seeing your setup.

On the other hand, if it still feels firm on the floor, then it's likely that your original setup was allowing the mattress to sag a bit. Since you liked it, this would imply that perhaps your body needed a bit of sag to get adequate conformance from a mattress that doesn't ordinarily provide adequate conformance for your needs. This would be a sign that your mattress is not actually a good match for you. At the same time, your experience with your previous setup would also provide a clue as to how you could jerry-rig it to work for you for at least some period of time.

I hope that's helpful.