Good enough plan?

Okay so my boyf left his fb logged in on my phone and I wasn't aware, it said a guy sent 2 photos so thinking it was mine I opened it and seen it was my boyf sitting next to a girl at his house, anywaysss I've heard he got with her. It's a girl who is known for going from guys to guy. The night the photo was, was the night we were on a break but agreed still together ( not act single) and he said he wouldn't do anything to harm us

ANYWAYYYY I then seen he deleted the convo with that guy, so I logged out and haven't been back on since. But I saved the photos. I don't wanna tell him I got them from his Facebook,

My plan is to make a fake Instagram and dm them to my real Insta, then deactivate the fake Insta account so it seems like it was sent to me. And then I'll confront him about it.

I'm aware I sound a little crazy but I don't wanna tell him I got it off his account because I already said I didn't go on it. ( forgot that I did ) and he's not very understanding so I need a plan that will work.

Should I just send the photos. Or should I say something too?

Guys help!!