Unusual spike in data usage

With a quick search I see there have been quite a few posts on this topic but all are now closed. Well, add me to the list. In October i got a text saying we were close to using all our data...honestly didn't even know we had a cap and i thought the text was a scam so i ignored it. However, about mid Nov i started getting the texts again (which i ignored) but by the third week in Nov i got a text saying we had used all our data...which i believe is 1229gigs. That's when i started searching around and found it wasn't a scam (at least the texts anyway) That's when i logged into my Xfinity account, searched data usage and i could then see our data history but only back 6 months. We used less then 500gigs June thru Sept. We hit 900gigs in Oct (when i got the first text), then 1800gigs in Nov and now third week in Dec we are close to exceeding the plan again. I have had Comcast close to 20 years and up until this past Sept, never knew i had a data cap nor had i ever been notified that i was close to reaching my limit...in 20 years! Then suddenly three months in a row we are over or close to? Something isn't adding up. So tomorrow i'll get to spend a ridiculous amount of time trying to speak with an actual person within Comcast...awesome.