ok i finally figured out wat it is. i used the process of elimination

. first i just let my mum play her yahoo games for one day and i didnt use the internet and it used like 13 mb. then today i looked at just cars and motorbike pictures and it used 287mb and hasnt finished updating. so the end solution is that it was the photos that i was lookin at that was doin it. and they take a hell of alot of downloads. thanks for the help anyway.