Sh8wty,
It oftens takes a lot more than just intercourse to make a gal orgasm. This is true for me in particular. Many times we will orgasm through other forms of stimulation, such as the guy's hands caressing us or his mouth providing oral stimulation, etc. Personally I find intercourse as just a means to the end of me but not the end itself, although the guy loves it and will typically orgasm.
Also you shouldn't get so concerned about your mind wandering or not necessarily thinking about sex at various times and don't forget that most guys minds will wander as well.
Lastly, don't be overly concerned about how you will 'perform' during sex as this will cause undue stress and anxiety which will only harm your getting in the mood.
I hope this helps,
Wendy