Monthly internet usage jumped from 75% to 90% in 2 hours

Hello,

I was out earlier tonight and got an email saying that I have reached 75% of my data usage for the month. Considering that the month is nearly over I did not worry about it much. About 2 hours later I got home and received a second email saying I have now reached 90% of my data usage for the month. Needless to say, it seems odd that so much usage would occur in so short a time without my being home. Is it possible to get more details on what is causing this?

Thanks,

Cory