Like others have said Moroccan Argan oil Mask from Superdrug. Massage into your hair and leave overnight. Gentle hydrating shampoo and conditioner such as Faith in Nature Coconut, Holland and Barrat.
Don’t rub after washing, Pat excess water out. Then with your hands rub through with Argan oil hair treatment, very small amount, from boots. Comb through with a wide tooth comb. Air dry until almost damp then gentle styling with the dryer.
Hair and mail supplements will help, but need several moths to really make a difference.
Also have a blood test.