8wks but scanned 4wks

Hi mommies.. Just in case ada mommies yg ada pengalaman sama. (pls share) Kalau ikut kn last menstrual, usia kandungan dh 8mgu. then, recently I ada spotting/bleeding (up to 6days already). I pegi cek kat doc. n doc scan, saiz kandungan bru 4mgu. Is it normal? Rasa takut la pulaaaaa.. Doc cakap, either I salah kira or baby tu dh stop growing. I harap sangat yg baby tu survive..