What Causes Skin Covering On The Vaginal Opening?

I dont know how to explain this...Ive had two kids . I looked in a mirror down there and I can see thick skin inside my vagina hole it covers most of my hole . I can push it in I dont know what it is and I can see some tears of skin too, I am by no means loose from having children the dr told me I have very strong pelvic muscles ... what could these be? I can make it move out more if I push like Im having a baby ?