too much to take

I'm married. 5 years. How do you determine too much to file for a separation? The reason I ask is because my husband has lost my trust. I found out he has been texting a woman and sexting her. Plus it's like we just can't talk about anything anymore without arguing. I've so far stayed because of our 8 month old son to try. But it's like it's getting worse. I never thought I could possibly be in a situation like this. It's like I don't even know him anymore. I'm just tired of the locked phones. No talking. Like we just tolerating each other. When I tried to walk away 6 months ago, he convinced me to stay. But it's still the same. Should I file for a separation?