Hair loss

Alright I know that shedding hair is normal for people. But recently I found a bald spot in the back of my head. It's completely bald!! But there are little hairs growing back. I went to the doctor and all she gave me was PRENATALS?? I'm starting to freak out because I don't even know what's wrong with me. And I was combing through my hair with my fingers and a bunch of my hair just fell out into my palm. Can someone help me please.