@the guy who thinks her cervix is "popping open"
lol I doubt her cervix is popping open and you are fucking the length of her cervix and into her uterus. I'm not a doctor but I find that ludicrous. More likely her body is reacting to cervical contact by lengthening the vaginal canal to accommodate. The pussy is indeed amazing 
It doesn't require a huge dick it's a variance thing. Average penis size is 5-5.7 inches and average vaginal canal is 3-4 inches which expands to 7-9 inches upon arousal as the cervix and uterus ascend. Some women's canals are 6 inches when aroused, others are 10 inches.
I am not enormous but I bottom out sometimes as, depending upon the position and how aroused she is, the vaginal canal can be more or less lengthened as the cervix and uterus ascend.
Also, at different times of the month the cervix can be more or less ascended and the texture changes as well. So sometimes it feels like a sharpish beak and others it feels more soft and spongy. It depends, I believe, on the ovulation cycle.
I had a girlfriend who had a short vaginal canal and I would bump her cervix in all deeply penetrating positions. Her best orgasms occurred when she could be on top and literally grind me deep inside hitting a spot on her frontal wall and on her cervical opening. It actually hurt the first few (dozen) times, but I got used to it. I could always tell by the feel if I had hit the exact spot she liked the best, and learned to hit it from other positions.
