suddenly swollen ankles

Sorry this is long, worried about my ankles swelling. I'm 30+5 weeks pregnant with my first baby and haven't had any swelling up till this point except for some swelling in my fingers. My ankles have always been slim and I've always been able to see my ankle bones on both sides. Today I looked down and both my ankles were way bigger than they usually are. Couldn't see my ankle bones and my ankles just went straight from calf to feet, no distinction. My socks were tight so I took them off thinking it would help but a few hours later now and it's just gotten worse. Right now my ankles are wider than my feet and it's worrying me because it just showed up all of the sudden. My ankles were skinny yesterday and then today they suddenly swelled to this size. Is sudden swelling like this normal this late into pregnancy? Does anybody have any advice or ways to cut down on this? All help is appreciated.