Hello everyone!

I have pretty frustrating problem, which I doubt is too rare but is frustrating nonetheless.

When I sit on a chair (normal one, without cushioning, no manger's or herman miller etc.), after around 30-40 minutes, when I get up, my legs feel "tighter". When I move around I feel it especially and its unpleasant. It's like there is more pressure inside of them and it makes it more difficult and uncomfortable to . I don't have much swelling ( I have some water retention after a nasty infection from which I lost some protein ) and I don't feel this sensation when I exercise for a hour or walk for 2. It's just when I sit on such chairs AND on flights. Several months ago I was on trans-Atlantic 12 hour flight and needless to say, it was bad experience for my feet. After I got off the plane, both my legs felt like they're going to EXPLODE! It was painful to even walk at normal pace. There was no change in the colour of my legs or anything and after 2 days their circumference and feeling went back to normal state, but WHY is this happening to me? What are the possible causes besides blocked arteries (which I am sure don't have), water retention and other stuff. Blood circulation? 

What would be your advise? (I'll go to doctor soon, so without whiz one, please)