Hello, Welcome to healthcare magic. Severe hair loss over few months is called telogen effluvium. It is a hair loss pattern usually triggered by a physical illness (like viral fever, typhoid fever, hepatitis, etc), stress, crash dieting, weight loss, child birth and surgery which you would have about 3 - 6 months prior to onset of hair fall. It could also be due to underlying anaemia and thyroid abnormalities. Weight gain and inability to loose weight inspite of a normal apetite and exercise could indicate an underlying hypothyroidism. You need to check your hemoglobin levels, serum ferritin levels and thyroid status. For hair loss, You could take vitamin supplements containing biotin, calcium pantothenate and minerals for a duration of atleast 3 months. Hope this helps you. Take care.