I think all marriages are with ups and downs, i dont't think there are any relationships with no issues. you are not alone. I believe it is like that for some mummies here as well.
Its normal to feel wear out when probs kept coming and you mentioned you have got 3 kids? How old are they? Are you working full time? Maybe you and your hubby can consider to have a heart-to-heart talk? Or maybe even attend a marital counselling??