I sure have been there! First step I do when I feel like this is pay attention to how much sleep I've actually been getting, how much exercise and what I've been eating lately (iron? folic acid? junk food (my downfall!)) Then I try to remember the last time I had a moment of peace...and I try to get away for at least a few minutes for a quiet time...usually reading my Bible....lifting up in prayer, my kids, my husband (and me)....hmm a cup of Tension Tamer tea sounds good about now...
Adding a time (even if brief) where you can center yourself and regroup during the day really helps.
I love books by Sally Clarkson, because she reminds me that this motherhood journey is a marathon and we need to get refreshment along the way so we have something left in the end. www.wholeheart.org Dancing with My Father is her latest book, and I also enjoyed Mom Walk and Seasons of a Mother's Heart.