How many women can come through penetration alone? All the time? some of the time? Never?

I guess I'm in the minority of women who can always orgasm through penetration. I had an orgasm the very first time I had intercourse and I have had one every single time since, without exception. Before I started having intercourse, the guy I was with used to lick my clit all the time and had made me come that way a zillion times, plus I'd been masturbating forever. So I figured that when we started fucking it would be hard for me to get there. Well, I was very mistaken. The very first time he entered me, as he progressed slowly in, that sweet feeling in my vagina welled up as he filled me and just kept building with each thrust 'til I finally exploded. It's always that way, every time, regardless of who I'm with. Some guys will reach down and start playing with my clit while they're thrusting, thinking that I need that to come, but I'll pull their hand away-I'll say, "that's ok, baby, don't worry about me" If my clit is stimulated during fucking, it seems to shift the feeling away from the vagina and messes up everything. I just tell him "you wanna make me come, just drive it in hard" It actually doesn't have to be hard-that'll just make me come quicker.I kind of have a theory about it-my vagina is kind of tight, due to my small stature, and I think I feel filled easier than many women. My sister and I have talked about that, and she's somewhat bigger than I am and says she doesn't feel as much during intercourse-she always has to stimulate her clit to come. She also is more tender-her boyfriend has to be careful not to hurt her when he's thrusting-with me, just tear me up, nothing's going to hurt me-the rougher the better. My sister and I have made love with our boyfriends in the same room several times when we go on vaction together, and after they've been fucking for a while I'll start to hear this rhythmic, swishing sound-that's her rubbing her clit back and forth, and finally she'll star to go "errrrrrr" and I know she's losing it-that usually sets off the rest of us. Anyway, I'm curious to know everybody's take on this.