My hair has been falling out very bad. Why is this?

Multiple reasons. There are a variety of reasons hair falls out. These include poor diet, stress and improper chemical treatments to your hair. Internal abnormalities can also affect hair growth including thyroid disorders, iron deficiency, low B12 and other hormone disorders. The best thing to do is have a complete workup by a board dermatologist who will help you identify the problem.
Hair falling out. There are many possibilites. What is going on in your life. Hair falling out can be nutritional, hormonal, disease or normal things like pregnancy etc. Please re-ask with more specific information so you can get help. Otherwise see your doctor for a checkup.
Hair loss. Hair loss, if sudden, can be a delayed result from significant bodily stress, emotional or physical, from three months prior. The hairs grow normally in three different phases and shock to the system makes them grow in the same phase. When the new growing hair pushes up, the resting hairs fall out. So when you think you're losing your hair it's really growing back. Normal loss is 200 per day.