I'm sorry I know this feeling...'if I took another decision now I'd be doing something that I like, and instead I have to do this'...it's not a nice feeling at all.
But don't worry, it's not forever And I don't think that your parents expect that it is. But probably it's true that they wouldn't agree if you quit the job very soon. How long have you planned to do it? You could say to your parents that you don't like the job very much, but you'll try to finish the period that you had decided. If you didn't plan a period you could plan it now, with your parents. Maybe till you go back to school. And you could say them that you have intention to work again in future, but doing something else, like baby sitting. I think that they'll agree.
I think that it hasn't been a so bad decision, however. At least you have tried. If not you couldn't know if you like this kind of job or not. You have to be proud of yourself for having had the courage to try a new experience.