What Causes Thinning Of Hair?

It appears my hair feels thinner. It falls out in large strands when I brush or wash it. There are no bald patches but it feels thinner overall. I am age 42 and my periods have been heavier for first three days. I don't have any other symptoms. My haidresser noticed my hair was thinner. I did have a thyroid test last year and it was all good. I was thinking it could bs stress because I'm
Self employed with 140 employees and work never ends or maybe hormonal changes being that I'm getting older. Any thoughts?