Female hair loss at 41 yrs old need doctor advice

[Joelle]

I am so confused about what to do about my hair loss. I am 41 years old and have been slowly loosing hair since I had my last child. He will be 5 years old in March 2010. I am adopted and unfortunately the state of NY allows me NOTHING to help me with my family history.
I went to a dermatologist who was of very little help to me. She told me to take vitamins, (b-50, calcium, multi vit. and biotin, I also take fish oil). I have taken them for over 2 months now with nothing noticeable as far as stopping my hair loss or re growth. I use to have very thick hair, but now it's to thin. If there is a light above me and you look up under my bangs, you can see how thin my hair is. I have included a couple pictures.
My question is, what else can I do? I have been taking birth control on and off since I was about 21 years old. Can that be causing it? I had test that said my thyroid was fine, no apparent problems there.
Please help me.