Hi Kim,
I am 50 years old and all my life I have had hair fall out when brushing dry hair. When I wash my hair in the shower, some falls out when it is wet. I suggest going to a doctor first, and possibly a dermatoligst, as your scalp could need some vitamins that you are missing on a daily basis. I started taking a multi-vitamin every day and that helped with my hair loss and condition.
Can you give an idea on how much hair you are losing when you wash it? Is it handfuls, or some pieces that you find after washing it? Sometimes we scrub our scalps to hard and hair will drop out. Try a gentle massage, that is what I do, and see if that makes a difference. Also, there are natural shampoos with vitamins and herbs that strengthen hair. What shampoo do you use? Different shampoos make a difference to your scalp. Believe me, I have been there!
Good Luck and post your results, if you try what I have suggested. I hope this helps!