Need a little advice

If you were in a relationship with a man for two and a half years, and that man texted another woman flirting, but never text her again after the first time, could you forgive him? Take into account that the incident happened two weeks after you told him you were pregnant. At 9 months pregnant you found out this happened. You didn't know the entire time that the incident happened, and he lied to your face and said he didn't when you asked. All because he said he didn't feel the need to admit something that only happened once but wasn't pursued because he felt guilty and actually interested, and didn't want to lose his family because he had no real interest in the woman. What would you do about this situation? Is this cheating?