<human>: Can you provide a brief overview of the text?

My boyfriend and I have been together several months, it got serious very fast and we mutually decided to be exclusive almost immediately.  He's everything I never knew wanted in a man, and then some.  I've met his family and he wants to meet mine.  

I feel like we connect on every level physically and mentally, but I am losing sleep over one issue.  When we're together and he sends snaps of something funny, I am looking at his phone while he is selecting who to send it to, and I can see a girl I know he has dated back in November/December is on his 'best friends' list, at the bottom no less, but still bothersome. 

 I can see he's sent a pic to her within the last two weekd or so too.  To add some color, I think they met on tinder, have no mutual friends, and only casually dated.  I have no reason to believe he is/was still seeing her, and he's made it clear to me that I am a big priority in his life now.

Any advice on how to broad this subject? Am I being unreasonable if I tell him his snapchatting his exes makes me uncomfortable?

  I need to talk to him about it, because I'm starting to lose sleep over it.  I'd rather not come across as super jealous and controlling.
<bot>: BF is exchanging snaps with girl he previously dated causally, I am going crazy with jealousy.  How can I/Should I kindly bring this up with him?