Inability to orgasm !

So I'm a 20 year old female, who is bi sexual, and regardless of who I'm having sex with (male, female, my current partner of 2 years), I can't "naturally orgasm", as in my body doesn't just "allow it" to happen. I mean, it's happened a RARE amount of times, but generally I just can't ! And it's not about my sleeping patterns or diet or exercise abilities or anything, cos I am physical fine with all of these things!

I have to either fake it totally or distract my partner n start doing things to her, so that she forgets about me for a while...I HATE IT.

Our sex life is SO SHIT because of it. And I just don't understand why, but I'm ALWAYS horny, I ALWAYS initiate sex, etc, BUT I can't ever cum. I masturbate every morning and night and cum within a few minutes, so I know my sex drive is all fine n dandy!

DOES ANYONE ELSE HAVE THIS PROBLEM ?!?!?!

I feel like I'm the only one !!! It's definitely not my partner cos I have orgasmed on the rare occasion with her, and I've had quite a few sexual partners and I have orgasmed a few times with them too in the past, but only when I'm really busting to pee or something (for some reason this increases my ability to orgasm lol but i cant exactly make sure i need to pee every time i go to have sex...thats gross!)

HELP !