I agree that improper chair height can be a real problem. If you machine sits above the table (not down into a cabinet) then you need a really high chair. You never want to have to hold your arms up higher than, or even level with, your shoulders. This can impinge nerves in your neck.
As for your back, do you get regular exercise? People who are more muscularly toned and flexible will have the natural spine support of those fit muscles. So try some weight training exercises and stretching, like yoga-- regularly. It does make a difference in your spine health. Then take frequent breaks, straighten up, and roll your shoulders backwards a few times. Even backwards bending while in your chair is a really great relief for your spine.