stress or mal nutrients are a common cause related to hair loss scalp problems, try to find a tricologist they will be more inform than a dermatologist on these matters, I woke up once and my hair hair practically gone my was alopecia and although not herditry it stemmed from an accident 6months prior as the way hair folicles grow is slow and when the body takes nutrients the hair is the first place it goes to, thus when the hair breaks through the scalp the strands are not strong enough to hold the remaining hair resulting in the loss so maybe think back a few months and see if there was any trauma or mass stress in your life, usually hair growth is cycled so hopefully for you like mine it will grow back

I was advised by my tricologist though that no lotions or potions will help only time and a stress less and well balanced diet approach