Husband thinks i cheated but didn’t

Little back story, my husband and I split up earlier this year and have recently decided to try to work things out. Taking it slow and trying our best to make sure this is in the best interest of everyone. While we were split up I thought it was for good. Never in a million years did I think we would try to work things out. I ran into a friend from high school and we would hang out and casually started dating. Nothing serious. I broke it off because he wanted more than I did. Fast forward to husband and I working on things for almost 2 months and tonight he brings up that I had a different timeline than I’m telling him. He’s telling me that he had A LOT of people telling him I was cheating on him and talking to other guys and I was out having fun and all this stuff. We have 6 kids together (4 kids under 4) and I work full time. He was on 3rd shift at the time. I didn’t have time to get my nails done let alone go find someone to cheat on him with. I would never cheat on him. The thought never even crossed my mind. I’m so heartbroken to hear that he truly believes these other people, who he won’t name, over me. I dated one person while we were separated and it was never more than dinner. Never slept over at the others house nothing like that ever. I just don’t know what to say to him to get him to understand that I would never have done that to him at all. He won’t even listen or try to listen to what I have to say. He just talks right over me and won’t even try to reason with me at all.