The pelvic outlet has 3 joints, one either side of where the sacrum joins at the back and one at the fron where your pubic bones join (symphsis pubis). The sacrum is also able to swing back like a hinge.

During late pregnancy you make lots of ahormone called relaxin, which makes these joints muhc more flexible, and in labour you get and extra boost to make them even more so, so yes the pelvis gets much bigger.

Which part of your pelvis are you feeling during your explorations? One fun thing i learned when PG was to try to touch the back of the pubic arch (about where i pee from) and my tailbone, with the same hand while standing up (i used my thumb for the pubic bone and my littlest finger to stretch to the tailbone), and then bend over so my thighs and back are at a 90 degree angle. I could no longer reach my tailbone because just bending over not in labour opened my pelvis so much more!

Bx