Hi Timmdogg,
A fiber topper or mattress pad (see post #10 here) can add a little bit of additional cushioning under your pressure points but they are not as resilient as a foam topper and don’t redistribute weight along the sleeping surface of your body as well as foam. They are more for “feel” than overall pressure relief.
If you are looking for pressure relief more than “feel” (which it appears you are) then a foam topper would probably be a better choice. There are some topper guidelines here that may be helpful.
A mattress that is too firm for your specific needs and preferences is just as likely to cause discomfort, pain, or alignment issues as a mattress that is too firm (see post #2 here). The goal is always to find a mattress that is “right” for you in terms of PPP. Our ancestors had very different lifestyles than we did and there are many people who would suggest a softer mattress with certain types of back issues. The “old days” of suggesting firmer mattresses for all back issues are long over as it was understood that contouring support that keeps the spine in alignment is much more important than firmer support. It’s also important to remember that primary support/alignment comes from the deeper layers of the mattress and each person also needs suitable comfort layers that can relieve pressure in all their sleeping positions.
There is more in post #2 here about mattresses that are too firm but the normal break in period of a mattress is usually in the range of 30 - 90 days (sometimes sooner and rarely longer). If after a month or so or even a little sooner it’s clear to you that things aren’t improving (or are getting worse) then it’s quite likely that the mattress isn’t suitable or at least not ideal for you.
Phoenix