I agree checking with a doctor but also look into massaging a good oil in your hair/scalp at least twice a week. I just recently started using Jamaican Black Castor oil. I've heard it thickens hair but obviously can't comment on my experience since I've only used it twice so far. Google search essential oils and you'll come across some great info on oils that will stimulate your scalp and help with hair growth.
Also, take a good multivitamin daily and drink lots of water. Hope that helps!