Odd swelling? Or maybe this is normal?

I am a teacher. I am on my feet all day, up and down off the ground and moving about. When I get home I usually rest, but sometimes I cook dinner or run to the store or whatever. Anyways, I don't have any swelling. However, the last 3 weeks, my feet and legs have swelled up on Saturday. A day that I spend lounging around, hanging out with my family. I take a nap in the afternoon, and when I wake up, my feet, ankles and calves are decently swollen. Is it the week catching up to me? Is it the lack of movement? They're pretty bad tonight, photo for reference.