Bruised feeling (but not) labia?

I'm 33 weeks and my labia majora feel bruised much of the time now, but especially in the mornings or if I've been sitting at my desk for a while. But they only feel bruised, they aren't actually bruised. And they only feel bruised on the inside, meaning if I touch the skin it isn't bruised feeling. 
This sensation is difficult to explain, but I've had this feeling for several weeks, maybe since 28 weeks or so. It seems like it's gotten worse or more intense as I've gotten bigger. Anyone else feel this? Or know what is causing this? It doesn't really hurt and I'm not worried about it, just curious.