Why is my hair falling out so much?

I have medium sized,black,straight hair. I don't straighten it, blow dry it, or mess with it other that combing it and the occasional hair care product. My hair is very healthy and I have no problem with it other than the fact that it is falling out. Don't get me wrong, I have ALOT of hair. I'd compare it to a cat shedding its fur, you really cant notice it. Its not like its getting thinner. I was just wondering why it is falling out so much. If i run my fingers thru my hair, strands will just fall out. My hair grows incredibly fast so I dont think it has anything to do with my health. I appreciate you taking the time to read this and would like your expertise on this and/or a product I can buy that will stop this. Thank you!