I'd only use apprehensions if there was more than one reason I was apprehensive.
I'm not sure I want my daughters to go camping this weekend. The weather is supposed to be terrible, I'm not sure their old enough to handle a weekend by themselves, and there's been a rash of crime at the park. Besides, they're exhausted from swim practices all week – I have several apprehensions about this trip.
Such a usage would be rare, however. I'd usually be inclined to group all those worries and concerns together, and say, "I have much apprehension about this trip."
FWIW, a half-century search in Google books returned less than a dozen results.