Can you find something less stressful? If so, considering you're an introvert and sensitive, I would (I say that as someone with a similar personality!). I mean, it's a tough call... if you know it's a temporary thing ("it's stressful, but I've only got to hang in there for 6 months until I've got the money to go overseas...") it might make it more bearable?

I also sort of wonder though... if you want to be an au pair, would it make more sense to look for work now that involves kids (for the experience)? Would that be less stressful, and more relevant?

Good luck!