This happened to me, and I'm only 20! I had three 1-2 month periods where my hair fell out like CRAZY. I was so upset and distressed--I take multivitamins AND a supplement with crazy amounts of biotin and I was still losing handfuls. Finally, I connected the hair-loss periods to a condition called telogen effluvium that happens after an event of enormous stress on your body. I had had two different surgeries and a kidney infection that brought me to a fever of>105. It can be medical (like mine) or an event that happens that gives you copious amounts of stress/grief/etc.This stressful event (even if an illness wasn't mentally "stressful" to you, a high fever/surgery/bad infection/etc is still stressful to your body!) "shocks" the hairs on your head in resting phase to kind of shut down and around 2-4 months later, large amounts of hair fall out. If you've been having a series of stressors in your life, it may continue instead of stopping after a (very long) month or two. There's nothing you can do to stop/prevent TE if your body/mind has gone through large amounts of stress, but you can look to see what medical condition, life events, etc are putting stress on you.

That being said, you still may want to see your doc if you haven't in a while. Hair loss could be a result of a nutrient deficiency, thyroid disorder, or a myriad of other things. They can run a blood test to make sure that you don't have any underlying illnesses that may have more severe consequences than hair loss!
Good luck, and if you want to PM me, I'd be happy to give some support/advice on managing that kind of hair loss and thinning!
3a w/ 3b underlayers
Low-normal porosity, regular-coarse
Recovering from TE
Products: Suave Naturals (co-wash), Kenra Moisturizing Conditioner, Fast Food (leave in), SM Curl Milk, Devacurl Light Defining Gel, coconut oil
(Product use varies according to weather, time constraints, and desired look )