I have had two episodes of fairly heavy vaginal bleeding in the last week, passing fairly good sized clots each time. Should I go to er

What do you consider a "good sized clot?"

About half a fist size

Also, my legs and feet are quite swollen, with some discoloration of my feet, and some numbness and tingling in my toes

Yes.

It is hard to say what the clot is. There are possibilities. You should REALLY go a seek professional medical help.