My bf used for have a school crush, he talks to her occasionally, he told me about this, but I didn't know about what they talk. One day he logged in his insta on my phone and forgot about it. I used his insta fir few minutes, to see his chats with his crush. He talked to her on the day we fought, and flirted with her, the flirting was cheap and leading. I closed the chat, did not read further. I told him that i didn't see anything, and logged out his account. Now I don't know how to proceed, should I enroach the subject and tell him I saw it, or should I just ignore the whole incident itself as insignificant, or should I bring the topic on and see if he tells the truth or not, without telling him that I know about the chats?