I don't know how far along you are, but I definitely felt like my vagina was going to fall out in the last couple of weeks--oh, the indignities visited upon us by pregnancy .
I had my daughter at 37.5 weeks and had done modified Jazzercise until 35 weeks...then it was just too much pressure on everything. I also felt like I could feel the two ends of my pubic bones rubbing against each other...most likely ligaments stretching.
Anything unusual is also worth a call to your midwife or OB, but it doesn't sound all that alarming to me.