When to call it quits

I started working about 2 months ago and since then my health has gone downhill and the stress on my family seems to have escalated.  My husband works a very demanding job in Manhattan and is gone 7am-7pm so I am the main caregiver of the 2 kids and now I work part-time Monday, Wednesday and Fridays 9:30-4:30.  This doesn't seem like many hours but it does seem to be taking a toll on both myself and my family.  Our weekends, which used to be nice and relaxing, are now spent running around like chickens with our heads cut off and I spend every evening falling asleep on the couch by 8pm, barely spending anytime with my husband.
I'm not working for the money, as I'm not making much, but I do love the job and am enjoying being "me" instead of just mommy and wife however I don't know if the toll is too much.   How do I know when enough is enough?  How do I know how to make the decision?
My plan for now is to give it another month or 6 weeks and if things don't improve then I may need to call it a day and quit.  I'm not a quitter but I'm not sure what other options I may have.