I can't tell if my new mattress topper is hurting my back

Ever since I bought a foam mattress to fix my aching back caused by super firm innnerspring bed, my back and neck have hurt in different ways. My lower back has been in pain for weeks now. I’m sinking into the bed nicely at night and it feels really comfortable, but I’m starting to think it’s the reason behind my back pain. Anyone else have a similar experience? I’m worried it’s the bed as a whole and it just needs to be outright replaced…