I don't know the answer since hair loss can result from lots of things...however:
1. Instead of taking selenium pills I eat organic raw brazil nuts daily. I eat about one or two a day but you could consider an ounce a day for a month to build up your selenium levels. Then decide how much to eat daily.
One benefit for you is it's nature's selenium that tastes good and comes with lots of other goodies that may be critical for assimilation. They sell them in my good health food store in the refrigerator in little bags.
2. I get hair loss when I don't eat meat. As soon as I make bone soup and have a couple days worth of heavy meat meals it stops. This would not be true for all people.
I actually use this as a metabolic typing guide that I need some meat protein. And it's red meat that stops it... I have no idea why.
I'm so sorry this is happening to you.
Love ya,
Suzanne