My internet consumption seems out of whack, what could it be?

I have a consumption limit of 250 gb per month. Since I started with this company 8 months ago I’ve never gone over, except in March. I was even gone for a whole week in March! And now I just checked and for 2 days of consumption I’ve used more than double what my levels usually are, even though I barely used wi-fi yesterday, didn’t watch any videos or do anything that uses a lot of data.

For the last days of March, it showed me using 15% of my data in like two days!

I live alone, and I’m gone for like 12 hours a day so I find this all hard to believe. I have a secure password, which now seems like it needs changed. What else could cause such a spike?