How do you guys sit in your computer chair, what position do you usually sit in and how far from the mouse & keyboard do you usually sit?

Why?

I'm asking this because at my job I am on the pc for about 8 hours everyday, and I sit up as straight as possible and keep the monitor at a distance, and the keyboard & mouse very close.

For some odd reason, my shoulders...the tops of them get this BURNING pain...like some injected thermite into my shoulders, No matter what position I sit in this pain persists, its been persisting for a good 3 months or so, and its REALLY starting to negatively effect me.

I will see a chiropractor soon hopefully, cause this pain is UNBEARABLE, I can hardly work anymore.