Game Data Usage
It must be something else, check your computer for viruses, because gw2 is something like 25 gb to download, and it requires so little bandwidth to play. While using skills and the sort, you’re maybe using a maximum of like 80kbps down and like 20kbps up, it’s really not much at all.
Do you live with sibblings or roommates? Because if you do, one of them has to be torrenting things. It is possible to disable P2P sharing with some routers, but it may prevent you from playing certain games that need it.
If not, make sure your router is using WPA2 encryption on your router, if you are using WEP encryption, you are vulnerable to attacks from outside, as a WEP key can be cracked in no time. In either case, I would change your wireless router password to be safe, as someone might have gotten in your network.
Sounds like ‘someone’ added quite a few movies to their OneDrive Folder.