I'm 15 years old and I've noticed that I've been losing a lot of hair recently. When I'm in the shower or brushing my hair I always lose some hair. And sometimes when I wake up there's 2 or 3 strands on my pillow.
I think my hair has gotten thinner than it used to be and I don't know why.

I'd REALLY like to know the cause and how to prevent further loss. Can someone PLEASE help me?