I just started using one of these. Today is day 4. (The weekend was in the way, so it's consecutive day 2) So far the only real change is my back is hurting in

I just started using one of these. Today is day 4. (The weekend was in the way, so it's consecutive day 2) So far the only real change is my back is hurting in a different place than with the cheap chair I had. (upper back instead of lower) I'm giving it till Friday because I've heard that back pain is normal at first mostly due to muscles being used that you weren't using before.