Spontaneous shedding & growth - what kind of hair loss am I suffering?

I began spontaneous, heavy shedding of hair from the top of my scalp in May 2020. It lasted for about four months, then the hair spontaneously grew back without treatment. Shortly thereafter, it resumed with a vengeance. I have suffered periods of extreme hair loss followed by regrowth ever since. A scalp biopsy did not reveal either TE or androgenetic alopecia. I have been under extreme, ongoing stress. What kind of hair loss am I suffering???