Decisions decisions, should I stay or should I go?

Confusing stuff all this number crunching! I now have the decision to make - should I stick it out at my work for another few months, full of stress and lots of change, or should I leave to become aupair for my brother (getting a wee bit of practice on the old baby front ;-b) but having some uncertainty of how long it will last depending on whether my sister in law gets another job and takes garden leave and doesn't need me anymore... Oh what to do?!?!