How do you know if you have permanent hair loss due to medication?

I took Yaz several years ago, and noticed I lost a LOT of my hair. Its curly and has always shed bad, but this was a lot all the time. I don’t have bald spots or anything, and still have medium thick hair, but about 2/3 of what it was.

Yaz now has a lawsuit against it, and one of the symptoms/problems is permanent hair loss. How do I know if that’s what caused it and how would I prove it?