Hello, since the second of march, according to iinets toolbox, i have been downloading about 15-20 GB a day which is absolutely preposterous because all i've downloaded since then is about 3 albums. mum has recently started using skype with a webcam and has around 20 minute sessions but she only started using it yesterday. The only other thing I've used internet for in the past few days is to browse websites like facebook, 4chan, memebase and a little bit of Omegle (regrettable decision) etc. I have also had about 2-3 games of Heroes of Newerth.
I am capped at the moment which is extremely annoying considering it was only reset 8 days ago. The only thing i can think of is that theres a virus or malware of some kind, or the webcam and skype. I've run scans with Microsoft Security Essentials and Malwarebytes, both results came back clean.
If you have wireless connection enabled to your network, I would start with the assumption that someone is using my bandwidth. I would set a new router ID and password, I would change my WPA2 passphrase, and enable MAC address filtering.