Losing too much weight while quitting

First time asking aomething like this, but I'm kinda starting to worry. I'm 19 and have been smoking hash for atleast 2 years (no idea when i started) last week i putt the bong down, but now im losing weight fast. I eat more than i used to but it just goes straight through me. the past week i've gone from 60kg to 57kg. For refrence, im 180cm tall and sit home doing nothing all day.

Is this normal and/or does anyone have any tips for gaining weight