Cheating

I recently found out that my boyfriend of a year was being unfaithful. He hasn’t been physically inappropriate with anyone but I found some Instagram messages where he had been flirting with a few women and then when they would compliment him back he would end the conversation. I was obviously very upset since we live together and he’s really active in my two year olds life. We talked about everything and he said it’s a validation problem and that he had no intention of sleeping with anyone, just wanted an ego boost. Should I leave him?