Swollen ankle/leg

Sydney
30 weeks pregnant. Leg & ankle is swollen and painful out of nowhere. Apparently people lately have a problem with these kinds of questions so before people jump down my throat my doctors office is closed and I don't want to sit in the er if it's nothing all night, my SO works 15 hour days & just got home to be back at 7... Does anyone know why or what it's caused from? Similar experiences? Outcome?