Something as basic as the way you sit at your desk every day could be contributing to general discomfort such as a sore neck, stiff shoulders, tension in the back muscles and swollen legs. This is especially detrimental for those of us who have to keep our butts parked in front of a computer every day for work. Sitting correctly will not only help alleviate neck and back pain, but it'll prevent bigger problems down the road, such as chronic lower back pain and permanently hunched, bad posture.
|My attempt at sketching.|
Of course, this all takes a little adjusting on your part, as not everyone's body is built the same. If your forearms are slanting up to meet the table, then lower the table or raise your chair. If this causes your legs to hang, get a small step stool or box to allow your feet rest comfortably against flat surface. Meanwhile, also invest in a good chair with a supportive back that will encourage you to sit straight without slouching.
By the way, there's no hard rule or scientific evidence as to how far away your computer screen should be from your face, but I personally think the idea distance is the length of your arm. So stick your arms out, and the tips of your fingers should just brush up against your computer monitor. From there, adjust brightness, contrast and font size to make viewing the text on the screen less taxing on your eyes.
Hope this was helpful!