T.B.
I just went through the same thing and i went to the doctors and had some blood taken and come to find out i had low iron (anemia). That also can cause excessive hair loss and you may even notice a few small bald patches on your head if you look throughout your hair. I would definately get some blood drawn. Pregnancy really causes alot of hormonal changes in your body. My hair is now grown in. Good luck and happy motherhood.
God bless,
T.