I'm SO sorry you are in the mess like the rest of us. I'm sure being pregnant has added a huge complication to your decision making process. Not that being pregnant is a bad thing. The pain is indescribable. Your Husband leaving his phone available to you is a good sign. Do you now have access to all email and social media accounts? He needs to be 100% transparent. No exceptions.
In regards to the text messages, I would not suggest that you read them. I asked many questions on D-day in regards to intimate details of actual acts my wife did with her AP. Holy S***, I wish she had not answered those questions. Those answers are now terrible videos that play in my mind often, and for a long time, constantly. If I were you I would have a VERY trusted friend read them and then tell you the filtered, non hurtful information. You don't want the chance of adding more pain than you already have.
Welcome to this forum. I hope it's helps you as much or more than it has helped me!
Male BS, D-day July 2015, trying to stay out of the dark.....