Hello! I suffered the same exact symptoms and I was about your age at the time. (I'm now 29).
I never quite figured out was it was because I was taking so many supplements with my iodine. I thought maybe it could have been due to incorrect Selenium or just detox. (I was taking both yeast selenium and Selenomethionine. Apparently yeast is not good for some people, so I stopped that but stayed with the other.) And while the hairloss/fall took a very long time to stop, my new hair growth is incredibly healthy and my few strands of grey/white did not return.
My advice is to not fret or stress too much. The hair will regrow more healthy and strong. I rarely get any hairfall now, maybe 20 strands per week, versus 100+ a day. But if I would suggest anything, it would be to possibly look at neem oil and eating a clove of raw garlic a day.
I do not recommend neem oil if you are trying to get pregnant, but it got rid of my parasites/tinea within a few weeks, and with that I noticed my hair was incredibly softer too. I don't use shampoo since my hairloss because I'm paranoid, only a baking soda rinse.
I also forgot about dry brushing (as per recommended) it is super helpful for the lymphatic system. There are tons of videos on youtube you can look up to learn more about different techniques. I will probably start this up again (ha).