There is a great book called "Prescription for nutritional healing" I bought in the healthfood store, but you can find it at ebay or amazon at a cheaper price which is a must have for any serious vegetarian or health conscious person. I was just reading the other day about headaches and some of the things they said you may want to try and avoid are carbohydrates, alcohol, dairy products, hard cheeses & tomatoes. Foods that contain the amino acid tyramine.
3000 ius of vitamin A is not too much and should not cause hair loss. Toxic amounts of vitamin A is closer to 100,000 IUS, but there is no need to take more than 10,000 really. Like "iamjen" said, low amounts of b vitamis can contribute to hair loss along with other things.
I have a question for you? Are you female and if so are you close to or going through menapause?