Cheating?

*posting this here too for alternate viewpoints*

Ok so I just need to get this off my chest because I’m essentially running around in mental circles of getting myself worked up and then calming down and marking my questions as a momentary bout of madness.

Anywho, my boyfriend and I know each other’s passcodes and switch phones and mess around often. I typically go on his Snapchat to take ridiculous pictures just for shits n giggles. Every time I go into his chats, I always see this girl’s name. By the looks of the times they message at least everdyay. Being the nosy person I am (I feel bad about snooping but I was wondering why he was messaging her so much) I opened the chat to find no messages. Only ever pictures sent back and forth between them, chats never saved, and the chat is the default “delete after reading.” Naturally this spooks me a little bit. My boyfriend is honestly such a sweet guy and I feel like he truly loves me, but I don’t know what to make of this. On Instagram he follows her but hasn’t liked any of her recent posts and she doesn’t follow him. Am I being paranoid? Or is this a valid cause of concern?