It is the heat. Drink a lot of water (i know, like you aren't peeing enough already ;) and put your feet up. The only 'cure' is delivery.

Going up at least one shoe size during pregnancy is very common. Your body is producing hormones that relax your ligments and allow your bones to spead. They will shrink back to normal eventually. Although, some women don't get their previous shape back ever (like your hips expand, etc).

Water! Water! Water! And feet up. It will get better when the heat subsides.

I hope so but its not like im always on my feet its too hot for that. Im usually in bed or sitting with my feet up, but I guess busy days like these make them worse