Okay, first of all, I'm not paranoid about my girlfriend faking orgasms. We are open enough with eachother that I don't have to worry about her lying about something like that after I askered her for the honest truth.
However, she is fairly inexperienced (as am I) and I wonder if she maybe just "thinks" she's having an orgasm. My reasons being:
1) She has like 3 every time we have sex... and I'm talking regular, missionary sex, with, perhaps, some oral foreplay,
2) I really don't know what I'm doing... I can never find the g-spot or clit and if I do find either I end up rubbing them the wrong way 
3) I'm not that "big." I know everyone says it's not the size that matters, and I've never measured, but I'm pretty sure it's less that average. Anyway, I'm lacking in girth and length, but then again she is fairly petite so I guess the two sort of cancel eachother out, (no?) Regardless, this is the least of my reasons, the other two, I think, are more valid.
She says her toes curl up and her back starts to arch and she feels all tingly, and she's on many occasions put some hefty scratches on my back (maybe I'm a massochist, but man I love that.) These all sound like orgasmic behaviour to me, but I don't see how it is possible that she could have orgasms so frequently and easily.
Is she misinturpretting something else as an orgasm? Or am I just one very lucky man with an even luckier girlfriend? 
if she's describing it as :
"her toes curl up and her back starts to arch and she feels all tingly, and she's on many occasions put some hefty scratches on my back (maybe I'm a massochist, but man I love that.)" then to my knowlegde she's having one hell of time from 'YOU'
You should take the advice of Brandye in that she doesnt need to orgasm to have sex! the act of sex is more than just to achieve an orgasm! its the idea of doing something together! Your looking at sex with too superficially. my g/f is the same, she's told me numerous times that she doesnt need to have an orgasm to 'enjoy sex'. having an orgasm is just a very big bonus (and wen she does, she does the things that your g/f does)
i reckon your a lucky guy, just like every ohter guy out there who has someone out there that loves them.
Dont Worry!!
Every girl is different, and most will prolly girls be jealous of how she can orgasm so many times!!
Does it matter? I have known women who had three children before they first experienced an orgasm. I often enjoy sex without an orgasm - sometimes do not even want one. The best experience for young women is masturbation. They tend to continue until they are satisfied and will eventually have a real orgasm. Then we know what we are looking for.
I was masturbating for a year before I had a real orgasm and then it was almost an accident and certainly unexpected. But ever after I knew what to expect. She will learn and in the meantime don't worry about it.