After a year and a half of dating and fucking, we found it! I was giving her a nice full body massage with our Shunga massage stuff and had her laying on her stomach. I was teasing her clit for a while and started to finger her a little. We have experimented before with no luck, but I was able to find it last night without a problem. It wasn't exactly what I thought it would be, as I was feeling for more of a mound. Her's feels like almost a muscle ligamant or tendon running horizontally that I can feel underneath her wall. She said it makes her feel like she has to pee, so according to everything I've read that was it. We didn't get a chance to play any more with it, as she just wanted me inside of her and I can't resist doing her from behind, especially all oiled up. But at lease we know and next weekend for massage time should be a little more fun!