why bother doing drugs?Can u stop?

I moved to a new area about eight months ago(2 my dads house in mid wales) i was fat and swotty and fed up of getting picked on so i decided to re-invent myself.
I went to a party with an old mate and all the cool people from school.They were all doing drugs so i tried it to fit in.
And i havent really looked back.Eva since then i have bin doing pills most friday nights going to partys smoking draw and not doing school work and i am LUVIN my life im loads thinner and look better and im worried that if i stop i might go back to my old ways.
No one suspects anything as i have always been such a good girl but i am starting to get a bit worried as i have tried to stop pills once before and didnt succeed i want to try again but am scraed that if i fail then it means im going to be doing them for ever.
Its such a hard choice as i am enjoying myself but i also know that i should be looking after myself better.I think i will probably just cut down or stop for a bit.
Also i still worry that people think i am sad and ugly but it seems that it just isnt true as i am mates with all the cool people.
Another thing is that im not sure that if i stop will i still be able to enjoy myself when i go out.I cant really imagine life without pills!