For me, doggie or any of the various on my knees variations, is about lust, raw desire, and sex. This is not the position I would choose if I were in the mood for slow, grinding, writhing, makin love, kind of sex.
I have a great g-spot vibe that has a curved tip. This makes it the perfect toy to access my clit while he is grabbing me by the hips and plunging in as deep as he can. I can even use the vibe to rub his shaft as he moves. I would highly recommend getting one if you spend alot of time on all fours.

Several times he has gotten out of the shower and found me on my knees, ass up using the vibe and let me tell you he is instantly turned to stone. Makes for an exciting encounter.
Since you can not remember having an orgasm that way maybe you need to. Next time you feel like masturbating do it on your knees and see how it goes.
Good luck! Keep us posted.
Oh one other thing.....doggie is a great position if you at all like hair play or having it pulled.mmmmmmmmmmmm