finasteride gave me the worst hair loss of my life, about 1 week after starting it. that is not normal and in the people that it occurs, it doesn't actually "regrow stronger" when it's shedding that soon.
if it's from the finasteride and you keep using it your hair will continue to shed but get better once you go off. it's rare but it happened to me, and a very small handful of men on hairloss forums (happens consistently, hair never gets better until going off finasteride)
could also be that prostaglandin, they do have some role in causing hairloss, depending on which prostaglandin it is.