is it normal to lose weight so fast? help

my favourite jumper, sized 16 — my sized — is now way too big and baggy on me :(. i usually weigh around 80kg but when i checked, i now weigh 76.5kg. is it normal to lose weight this fast? although i am eating healthier, i still eat junk (in moderations) and i don’t exercise and although i could just buy the same jumper again, i can’t due to lockdown and the shopping mall being in the next city.