Hello, Welcome to healthcare magic. Because of chemical straightening hair can fall, but it usually breaks from the margin of normal and straightened hair and do not fall from root. Sudden and heavy fall from roots is usually due to telogen effluvium.It is a hair loss pattern usually triggered by a stress- psychological or physical illness like viral fever, typhoid fever, hepatitis, etc which you would have about 3 - 6 months prior to onset of hair fall. It could also be due to underlying anaemia, thyroid abnormalities and after delivery. You need to check your hemoglobin levels, serum ferritin levels and thyroid status. Please have good diet including green leafy vegetables, eggs, dates. Vitamin supplements containing biotin, calcium pantothenate and minerals for a duration of atleast 3 months is the treatment of choice and get this prescribed by dermatologist. Better to avoid straightening of hair as it damages them. Hope this helped. Take care