General advice I can give you is to do some research into correct computer posture, a google search of those words should bring up a picture with the correct set up requirements for your station and also sitting posture. I would also try and work out a way to stop you having to have your chest on the desk and shoulders unsupported, maybe a cheap pair of glasses might help as well. I would also try and schedule in some breaks throughout the work day and do some stretches, an Internet search of desk stretches should help you out there. I wouldn't think those symptoms in your legs would be caused by poor posture so that is one thing again to flag with your physician.