Hi, i rem i had once read a manga about a fat girl who falls in love with a rich guy. But somehow, she met a car accident, causing her to undergo a plastic surgery, and when she recovered, she slim down and became pretty. I cant rem if its a one shot or not, anyone here knows which manga isit?

There is a Korean movie with this plot called 200 Pounds Beauty (Korean title: 미녀는 괴로워) I don't think it is based a manhwa).

The only other thing this reminds me of is Watashi ga Motete Dousu n da, which I'm pretty sure isn't what you are looking for (but might be similar).

Yea tatz not what i’m looking for.. was hoping someone had read tat before too~ its quite some time ago that i could not rem the name and whether isit a oneshot >.<

I don't know if it quite matches what you're looking for, but maybe Girls Saurus.

Could it be on of these two: Gold or Silver by Fujita Kazuko?

Maybe Helter Skelter