I had that very heavy pressure down on my vagina when I was close to the end of the pg.
I remember having the urge to squat to relieve the pressure - I'm not quite sure how that made me feel better but it did! I honestly think your body is stretching the muscles around the vagina preparing for labour (I always explained it to DH as an odd "stretchy" feeling). My labour was very quick and I only had minor tearing - hopefully this will mean the same for you!
Good Luck and happy hatching!