It sounds like a classical Pavlovian conditioned response. For some reason or another the computer has become associated with the physical problems. It hasa nothing whatsoever to do with emanations from the computer. The symptoms are real. Not imagined.
Btw, do you use the laptop for games of just watching a movie?
Especially when playing games, the symptoms you describe do occur. Because of the concentration needed for the game, cramping and staring and therefore also the effects of them are very common.
I do not think this is from electromagnetic radiation. At the distance you mention, radiation levels are so low that they are comparable to other radiation that is in the air from other things like power lines, mobile phone networks, radio and television, etc.
I think it has to do with you sitting in front of the TV in a cramped position.
Eye pain is from staring and not blinking enough, which also gives you headache. Lack of movement gives you knee pain and chest discomfort.