I did a bit of google legwork for you. I'm bored and somehow I've got to stay conscious all night. I uncovered the following:
If your hair fell out during a stressful period in your life you may have telogen effluvium. Something women get during childbirth or sometimes just during a particularly difficult time. Basically your body thinks something is seriously wrong because your emotions are going haywire. It shuts down unnecessary functions, such as the regrowth of hair. All those follicles that naturally tumble from your head on a daily basis stop growing back. You can test for it yourself by pinching about a dozen hairs or so and giving a sharp tug. If several come loose that's a good indicator. Do you have hairs on your pillow when you wake up in the morning? Check and count them. Also, do you find an abnormally large number of hairs in the drain after a shower?
The cure for telogen effluvium? Calming down. Which is about impossible when you think your hair is falling out, no? You're going to want to visit a dermatologist. He's probably going to need to take a sample of your scalp and send it off to a lab. I have absolutely no idea how much that would cost without insurance. A great deal I'd imagine. The important thing is not to wait. There are ways of slowing and even stopping hair loss. Regrowth, on the other hand, is extremely difficult.