One breast larger than the other?

Ever since about 7 weeks (I'm 18 weeks now) my breasts have been growing like CRAZY. They've never been this big. I started out at about a B and all I know is they are freaking massive now-- I was a C in high school and they are definitely bigger than that. The thing is, my left one is a lot bigger than my right! I know there is a wives tale saying that means you're having a girl-- and I am. But what sense does that make? Is anyone else experiencing this?