Webchick, I started shedding my hair a lot a few years ago until it ended up very wispy indeed.
I went to the doctor several times and he did blood tests. He couldn't find anything wrong other than slightly low ferritin levels. He said that if I wanted, I could go to a dermatologist at the local hospital (not on the NHS, of course). Almost as a last resort, he put me on iron tablets. They took a while to work, but eventually my hair started to grow back. I think I was on them for four months, but I am not totally sure, could be as many as six.
Now I am not on the iron tablets, he advised me to eat lots of iron rich foods to keep my levels up. I haven't been to him for over a year, because he doesn't know why it is actually falling out, so what is the point? Also, last time I went he mentioned if it was still falling out, investigating my bowels . I take a natural iron supplement daily now because I find it a much easier.
I suppose it has taken about 2 years to almost be as thick as it was before. I still shed a lot of hair but at least I grow new to replace it. I do nothing to it now, though. I wash it every other day, leave it to dry naturally if possible, only brush it if it looks wild. I have a dry cut at the hairdressers now because I could not face having it washed there and loads coming out. Its also a lot shorter than it used to be as when it was at its wispiest, it looked worse when it was long.
Obviously, this just worked for me, but you never know, it might work for you, too. I know its hard and I was impatient too, but it might be worth giving the iron tablets a few months before phoning a specialist salon.
Reading these stories does make you realise you are not the only one, but I don't think people know how awful it is.