unable to orgasm

I have never not been able to orgasm, it has always happened fairly easily! Last night we had sex and for the first time, not only did I not orgasm, but I felt ZERO pleasure. 
None.
Nada.
Zilch.
It kind of freaked me out. I kept thinking "what if I'll never be able to orgasm again??" 
But really, what the hell is going on? I'm supposed to be ovulating soon, so I'm usually more horny this time in my cycle than ever.