Forget the possible embarrassment of discovering you really did make a mistake — that might be what's bedeviling you the most right now. You get to try on this new job and see if it fits, because I promise you your employer is doing the same thing with you. Every job, whether it says so in the description or not, has a probationary period. And it almost doesn't matter what you're doing for those 16 hours a week (assuming you don't have to slaughter chickens or anything like that) — if the environment is great and the people you work with are fun, it could be great for you. If not, say goodbye; you have that right.