Women have a harder time enjoying oral sex than men. This happens for a number of reasons.
The least not being that the male has to be good at it for it to 'get the job done' more often than not. It takes practice for a guy to learn how to do this right.
Also, women are much more self-concious about their downstairs than males when it comes to oral sex. Do I smell? Am I too hairy? Can he breath ok? Is he enjoying it? This distracts from your ability to enjoy cunnilingus.
While it may simply be that oral sex is just not for you, it is more likely that there are other issues impeding your enjoyment of it.
Practice makes perfect, my hubby is very good at it- now.