When I insert a finger into my vagina I can easily feel my pelvic bones on either side near the entrance. Before giving birth I never noticed this. If I contract my muscles I can feel them move on top of the bone, but there seems to be only a very thin layer of tissue there, not thick and plump. What does this indicate?

It's funny I've recently noticed the exact same thing - the two ridges of bone on either side. I wonder however if I'm just much more aware now than pre-pop or whether the tissue really is thinner?
Perhaps an anatomy expert will chime in? I'm still waiting for my periods to start again and am curious to see how I'll be after they are regular again with 'normal' oestrogen. Will the tissues be plumper or is this another myth about hormonal the effects on the vagina?