YES! When my daughter was that old, I went for a haircut and even my stylist confirmed that this happens to everyone. He said, "Just wait till you go through weaning!" (but that turned out to not be so bad.) In addition to hormones, though, I think there are a few other perfectly logical factors that might have aggravated the situation. They might be worth a self-check:
1) Water! Your child is probably growing phenomenally at this age. Bigger kid=bigger appetite (often preceding another growth spurt!). Remember what you've heard about drinking 8 glasses of water a day? Forget it--you need a whole lot more than that to make up for what he's taking out of you (and for any coffee/tea/soda you've been drinking to stay conscious this long!) If you're dehydrated, that also means that your kidneys are having to struggle extra hard to filter out whatever's dragging you down. Help them out and rehydrate! (This usually takes 2 weeks of incessant sipping, so don't give up!)
2) Nutrition. You're probably doing fine here, but after those 9 months of treating my body like the baby-bearing temple that it was, the hectic pace of motherhood drove me toward quick snacks of convenience foods and vitamin drinks. Not much good for my energy, or for the immune power that my breastmilk was supposed to be passing on to my baby! You're probably still taking your vitamins, too; but your body (and your baby) needs lots of fresh food that still has its life in it--so next time jr. falls asleep in the car, pull over for the healthiest drive-through salad you can find, park in a shady spot with a nice view, and give yourself a break that really counts.
3) Sleep. Hmmm...let's get this straight...you're a new mother, and you're tired...new mother...tired...and you've been keeping it up heroically for 5-6 months. We ALL know what that can do to you! Add to that the possibility that you're sneaking what naps you can in an awkward position, when baby falls asleep on you nursing, and not only can you wake up cranky enough to pick a fight with a rabid badger, but you've possibly been moving your head all around trying to get comfortable, and--tah dah!--chronic new-momma bedhead, with no time to gently pamper those lovely locks back to shiny health. The hormones give a little push, and your frazzled hair falls out in clumps.
The hormones, no doubt, will take their toll; and I'm glad that so many other moms have written with their advice, concerns, and support. When you're trying so hard to take care of that busy little body and can scarcely find a moment to even go to the bathroom, sometimes you can forget to take care of your busy body, too. And like some others have said, don't add to the problem by stressing about it! Looking back, you already know how quickly things change in this new adventure of yours. This, too, shall pass; and with faith and prayer and lots of self-care, you'll come through strong and proud.
God bless you as you go forward with the most important job on earth!