4 Answers

Just sitting? But with stress? That could cause the discomfort you are asking about or it could be blockage.  See a trusted doctor..........

sitting around in a sedentary lifesyle  can definately cause aches and pains. So, get out there and walk !  But, before you do , you should get a clearance from your doctor. The motto of the old people is  " It's better to wear out  , than to rust out "

I agree. You need to ask your doctor. I wonder why you sit for a long time. I wonder what your stress is. You may not want to give this information. But someone might be able to help a little if you do say.  

if I sit for a long time, my body feels like I have Fibromyalgia. (I may have it) It gets achy achy achy. Let us know how you are doing.  : )

Yes. Posture is very important over time. It's better to sit upright than to slouch.