history: I took something from a boyfriend's house without him knowing. I think I should return it. I don't feel good about myself right now. I took something from a boyfriend's house without him knowing. Oops. Could you sneak it back in without him seeing you? I thought about that but I was thinking I would be honest and tell him what I did and why. Do you think I should? Depends how close you are and how mad he'll be. Usually_comma_ I advocate honesty_comma_ but don't know enough about your situation to advise.
current: Well, I think he is cheating on me so I took his spare I-phone that I suspect he is using to do it with! It is locked and I can't get in the phone to find the evidence.
next: Oh boy. I honestly don't know what to say. Maybe ask him outright if he's cheating. If he is, do you really want to stay with him? If not, it doesn't matter if he knows about the phone or not!