Boyfriend “stalking” exes social media

I lost my phone and my boyfriend let me use his work phone for 2 days until I got things sorted out. We’ve been dating for 9 month and never even had a disagreement, always been clear we’re looking for long term commitment, our relationship is great in every aspect.

So I started typing facebook in the search bar, because I tried to connect with my mom friend to set up a play date for our kids and I know no one’s phone number, and his recent Facebook visits popped up.

It was his ex wife (divorced 3 years, they share kids, but are not on good terms) and the ex after that, that he dated briefly (she supposedly ghosted him after 2 month). So my curiosity got the best of me and I checked his history, he has been looking both of them up at least 3-4 times a week, as well as their boyfriends, family members etc. He’s also been looking up all my family members and friends, and been checking my account daily even though I don’t even post on Facebook. And he’s only had this work phone for like 2 month and doesn’t use it much, I don’t even know what’s on his personal phone.

Plus, the day he gave me his phone he looked up how to clear Facebook and Google history (clearly didn’t do a good enough job…)

How do I go about this? Do I ask him why he’s looking them up all the time? Is this a red flag? I feel bad for snooping because I’m not that kind of person but it was right there in front of me and it really doesn’t sit right with me.

I really don’t know what to do, and before anyone asks we’re in our late 30s so social media by itself wouldn’t bother me, it’s just the frequency and extent.