New bed too firm - waking up with aching back

I recently purchased a Hypnos Ortho Wool mattress in firm tension having tried it in the Hypnos showroom. We previously had an orthopaedic mattress so are used a firmer bed. The mattress is on a new platform top ottoman base. Having had the mattress for 3 weeks, am finding that I am waking with lower back pain. We have been turning and rotating as per manufacturers instructions. Is it likely that the mattress with soften up or would a topper alleviate the issue?