Am I being bought as a follower? How to stop it?

I follow ~170 accounts. Today the section that shows the people I follow's stories has someone that I don't know. I go to check my profile and suddenly I am following 250+ people. I delete everyone I don't know (most of them have names that are random combinations of letters and numbers) and think that's it. 5 minutes ago, the same thing happens again. This time I'm following 280+ people??

I tried looking online if it's happening to anyone else but I don't see nothing. There haven't been any security alerts and all the devices registered to login are my own BUT I know It wasn't me following all this random accounts.