My 3g data useage has skyrocketed but I have not change the way I use my Ipad. Could this be a device fault ?

My monthly usage has gone from 1 to 2 gig/mth to 15+gig but I'm not doing anything differently. No downloads or hot spot just web browsing and email. I've changed my passwords just in case. It started around the time I upgraded to IOS8.3

Any know issues?

Could this be a hardware fault?