Sudden Massive Increase in Data Usage

I've never gone over the 1.2TB data cap, and have always been careful to monitor it.  I started noticing far more data usage on my acct a couple weeks ago when I started getting warnings about data usage (from Xfinity) much earlier than expected.  2 adults in the house, no kids.  Always use the same amount of data, mostly streaming TV.  

I just noticed today that the Xfinity app is now saying my data usage has suddenly spiked up to a massive 3.8TB, just within the last few days, and while I'm traveling away from home.  Something is seriously wrong here.  I'm being told that this will be my 1 month of data 'forgiveness' even though this crazy data spike is not from my house.  I need to get this resolved.  Thanks.