So that's one thing to discount as a possible cause :)
It sounds like you have an issue with low iron. Do you know what your Hb and ferritin are now? My Dr told me that for optimal hair growth ferritin should be about 75 and iron shouldn't be less than 120 (12 in old money).
As far as the dryness is concerned I can recommend using a coconut oil mask every other week. I buy pure coconut oil from Holland and Barret, it's the edible pure oil, not the stuff you get in the beauty sections with added perfume which is useless. I scrape out about 3-4 tablespoons and melt it in my hands and rub it all over my hair and scalp. I have thick shoulder length hair and this is a good amount for me. I tie it up and leave it on for a minimum of an hour and then wash it off with a mild shampoo like Moo and then use Moo conditioner on just the ends. It makes my hair very shiny and moisturised.
When I'm not using coconut oil I wash my hair with AsIAm cowash and use the matching AsIAm deep conditioning mask.
Every month or two I use something like Head and Shoulders to clear any build up.
I only wash/blow dry my hair once a week which I think is key to very healthy hair (as well as not colouring/perming it).
Also, do you take HRT? It can help with hair loss in some cases. When I started on HRT about a year ago for the first few months I lost lots of hair, evenly all over. It was like the hair loss you get after giving birth so no bald patches, but still alarming. I was getting seriously worried. After about 7 months it stopped and I got lots of new growth which has continued.
Ultimately, your hair issues like most things will be down to a combination of genes and diet/lifestyle. Do you see similar issues with other women in your family OP? How is your health in general? Are you on any long term medication? How is your diet?