Frustrated with sex

For the past 7 months sex between my gf and I has been almost non-existent.  When we first started dating, suprise suprise, we never left the bedroom.  We will have been together for 2 years in December and I'm worried that our sex life, or non-existence of, has reached the point of no return.

Here are the main issues.  I want someone who will just take me, do me with passion, not ask what I want.  She instigates sex by joking about it and using silly catch phrases.  She is constanty asking what I want, am I getting anywhere, is this doing anything, etc.  This completely ruins it for me, and I usually end up finishing the job myself, which leaves us both emotionally frustrated.  The gf is really shy about sex and makes jokes about it during and prior to.  This totally ruins it for me.  But, how do I say all of this?  Whey I try to talk to her about it, she turns it around saying that I'm constantly telling her no when she tries to "sex me up" (gahh!), and that our sex life sucks. 

And, when I try to have sex with her, she always squirms away, tightens her legs and other such things, and acts like everything hurts her.  I'm very aware of this, and try taking it slow, but I get really frustrated and tend to just give up after so long of trying to get her turned on.

At this point, most of the sex we have is with ourselves, which is frustrating and disappointing, and hurtful in itself.  I'm just not sure if we can move beyond this point, since we can't seem to talk about it.  And, for me at least, trying to and having to talk about it all the time ruins the excitement and suprise in it (...the things that really turn me on).

Advice please?!