Idk what to do.

Me and my significant other were getting ready to have sex when we realized we had no condoms. Well just so happened I had some old ones from a while ago that he bought. Apparently he forgot he bought them and flipped tf out. I kept telling him they were the ones he bought and that thy had been sitting in an old purse (a purse I recently started back using) for quite some time. Idk how else to get him to believe me. I honestly have not slept with anyone else the past year and a half that we've been together. Idk what to do. He's questioning who have I slept with. How can I make him believe me. I mean I know I can't but any advice ladies? I hate for this to tear us apart when I really haven't done anything.