"virgin territory"

I'll start. Recently I was was having sex with my girlfriend. I started to go really deep - deeper than I had ever gone with her before, because I finally got her to pull her legs all the back. She came harder than I had ever seen and she started crying in the middle of sex, but told me not to stop. Afterwards, she couldn't talk, she just held me and cried. I asked her if she was ok, and after a moment and a drink of water she said, "I've just never felt movement there before, it was amazing, you were in uncharted territory." Now she has her knees up next to her head every time we have sex.