Im lost

My son‘s mother just took my son and went back to her mother’s house after a fight we had she caught me texting with another girl. She saw that I said to this girl that I want her and tbh I do I find her really attractive and she is feeling me back but if I go for her, I lose my son

Before our son was born when she was about 5 to 6 months pregnant. on December 18 and 19 she slept with some other guy In his car. At first she said she was forced that was a lie.I forgave her for the sake of my son. I want him to grow up with a father. It’s so hard when I look at her too tell myself I’m happy and I can do this. I’m only doing it for my son. But since she took him tonight, I feel like I have a chance to end it. Her last text to me was “will come back home tomorrow and we’re gonna talk about if we’re gonna be together or not” I pray to God for my son and I have been put through hell