Ex boyfriend probs// sorry for the book, but ya girl needs help

okay,, there is this boy i’ve been dating on and off since 4th grade ( I’m 18 and graduated now) Recently, we’ve been talking. But I found out that he had sex with this girl, who while we were together and even after , he swore she would never be a problem. He did this while we just started talking again. his body count is 3 and mine is 1. I can’t stop thinking about it. I know we weren’t together but when i asked him about it,, he said his phone was broken so he couldn’t text me. But he text me a few hours later the night that it happened. He lied when i asked him if it was true,, then later he finally told the truth. Should I be upset about this? I know we weren’t together and it shouldn’t be my business but he makes my love life aside from him his business. Should I give him another chance?