Now that you have the proper chair, you need to use it properly:
1/ Both feet should be flat on floor which helps organize the spine upward.
2/ Legs not crossed (helps protect pelvis).
3/ Knees should be lower than hip sockets (takes strain off lower back).
4/ Pelvis should not be rolled back and creating a C lumbar curve.
5/ Spine should retain natural curves, but appear straight overall (ears over shoulder, shoulder over hip).
6/ Chest should be open for better breathing and digestions rather than collapsing.
7/ Eyes should be able to look at work or people within a 15 degree zone, not forced to look too far up or down.