Leg discolored swollen feet

So I've had super swollen feet for about 6 weeks now looks like golf balls on my ankles by the end of the day. My soles of my feet have been red most of my pregnancy as well and super itchy I'm 34w6d now. I know that this is all common, however today I noticed a weird discoloration on my calfs. I have my normal color on front and side of leg but on the back it looks like a huge white birthmark (that's all I can really compare it to). It goes from about 2 inches under my knee bend to 2 inches above my ankle, about 3 inches wide. Any ideas what it may be?