I added a thick foam mattress topper….man it definitely helped the sleep.Encourage you to evaluate your bed situation.
1) you have less weight related padding
2) your weight distribution is now different
3) your old mattress may have taken on your “old” shape.
I love really firm bed, but my hips started hurting because I’m skinnier and sleep on my side. Added a bit more padding on top of mattress and all good now.