Would you be angry if this happened to you?

A little while ago, there were a lot of rumours going around about me and my boyfriend (I'd been with him seven months, broke up with him the other day). There were people saying that he'd cheated on me with his ex, and it was all coming from people who'd know, not just people who'd want to spread rumours. His ex's sister found a lot of suggestive messages from him on her sisters phone and so she told me. Anyway, when I confronted him, he flat out denied it. All I said was that there was a lot of weird messages from him on her phone and straight up he starts saying 'I didn't root her, I didn't root her' and I didn't say anything about . When I said that it would be better if we weren't together, he seemed pretty indifferent. So, would you be angry if this happened to you, and do you think he was definitely cheating ?