how to make air travel more comfortable?

i have 17hr flight soon, 2 stopovers so each flight will be 5hr, 6hr and then another 6hrs.
I always get really uncomfortable on planes - i dont feel like throwing up but i lose my appetite completely, my legs hurt and feel restless, i feel soo tired and headachey. Is there anything i can do to help lessen the symptoms. I dont know why i feel this way...it happens on flights over 3hrs in length usually.

Maybe get some herbal sleeping tablets. so that they are not heavy and knock you out, they just relax you.

go to http://www.cheapflighttracker.com

The same thing happens to me in flights longer than 5 hrs. If you sleep it will make you worse when you get up. The only thing you can do is watch some movies in the plane or read a book or play with a gameboy.