I can guess what may be happening. It is likely one of two things (or possibly a bit of both). However as there are a few potentially more serious conditions that could trigger hairloss such as for example the onset of thyroid problems, my first advice, as medical student myself, would have to be to seek prompt proper medical advice please. Dont ignore this, it may not be anything serious, but it could just be the early warning which saves you from a more serious outcome. So do get checked over.
That said there are two pretty likely causes.
Firstly if you dont get the blend of hormones right you can get into a state known as estrogen dominance - which basically means the balance is wrong between androgens (yes women do have them and need them too!) progesterone and estrogen. Hair follicles are sensitive to this balance and will be unhappy if it is too far out, inducing what is known as female pattern baldness. Unlike male pattern this does not happen in one focal place - but produces a generalised thinning all over.
Luckilly this is usually reversible by getting a decent endocrinologist to monitor and properly titrate the dosages to your metabolism, which becomes ever more imperative the older you get. While self medication is never a good idea, it would be lunacy for someone older so I do hope thats not what you are doing.
The second effect that you may be noticing is that female hair while more plentiful than male hair, is generally of a finer grade - that is to say there are more hairs but they are thinner. Unfortunately when your hair loses its natural colour these finer hairs become translucent in a way that the thicker male hair does not, and so seem to disappear giving the illusion that you a losing hair when in fact your aren't. I had this happen to me in my 40's - and the solution was to simply colour my hair - which then makes the plenteous hair that I have properly visible again.
