I used to have lots of problems relating to premenstrual swelling of feet and ankles. Really bad. Good way to make an already crabby moody tired woman even crabbier LOL.

For this reason I think you should see your dr to rule out blood sugar, hormonal or like others said kidney or BP issues.

My swelling changed when I learnt about the principles of low-GI eating. This seems to suggest there was (for me) some sort of homonal-blood-sugar related effect. I also learnt how to pump my feet & ankles (like they tell you to when you're on a long airplane flight) as it's the specific squeezing of the calf muscles that helps the venous return. This might help when you get a chance to sit down.