Embarrassing problem with sex...

I have always known how to make myself orgasm, ever since I was little. It was never a product of any sort of trauma, I just happened to discover it accidentally when I was very young (maybe 3 or 4 hears old). The way that I discovered it was by humping pillows and the floor, essentially just pressing my vulva against a surface and moving it around, to reach orgasm (by clitoral stimulation).

I've added this topic anonymously as its very embarassing and I've never felt comfortable approaching the topic with anyone. I'm asking for help because it is causing a problem within my sex life. I love my SO very much, and I am very very sexually attracted to him and have no problem becoming aroused when I'm around him, but I can't orgasm with him. Vaginal sex does absolutely nothing for me in the way of stimulation, but I still enjoy sex because he gets so much out of it and I love being able to provide that for him. Sometimes he'll use his hands and apply pressure just the right way on my clit but it'll escalate to maybe 70% there, and I can't go past the edge of that, I can't finish. He asked me to show him how I get myself off so he can learn and do it that way, but because I masturbate so unconventionally (and am embarrassed about it) I can't show him "the right way". Its just a guessing game between the both of us.

Its starting to take a toll on his self esteem in the bedroom because he can't make his girlfriend cum, and I've tried to assure him that I don't mind and I'm not having sex with him because I only want orgasm, you know? I like the emotional aspect too. I need to know how to overcome this and compromise with him some how so our relationship doesn't suffer. Please, any help is appreciated. Thank you so much in advance.