Advice please?

Kristen • Pregnant with baby #3! My boyfriends first, it's new and exciting! Can't wait until August!
There is a girl that works with my boyfriend (the father of the child I am currently pregnant with). My boyfriend got promoted to a GM of a restaurant back in October and the girl that got picked as his assistant manager is a girl he has somewhat of a past with. They never had sex or messed around just sent flirty kind of sexting texts. The three of us used to work together, then she moved to a different store, then him and I started dating so I moved to a different store. Me and this girl were really good friends, but when we all separated we stopped talking so much. But I knew about their past with the talking and flirting. I still work at a different store but now the two of them are back working together and it is really getting to me. They text A LOT. I found a few flirtatious texts on his phone a few months ago. That was right after they started working together again and right after we found out I am pregnant with our first child together. Him telling her good morning and asking if she was mad that she wasn't there with him on certain mornings. Then talking about me like I am the worst person in the world. Telling her that he was out picking up dinner and happy that he wasn't at home. Since then he has apologized, bought me flowers, for the most part our relationship has gotten better. But I still can't bring myself to be comfortable with them working together. Am I crazy? Some days I'm fine. Her and I talk, we talked about the texts and she apologized. But she didn't really have a lot to do with them, he's the one who started it all and she had very short replies. But I can't get over it. I always want to look at his phone and read his messages to her. I love him to death and he has never cheated on me and I really don't think he ever will. But I don't know what to do to get this stuff out of my head. I want to be okay and I want to stop having the urges to look through his phone. I want to just be happy and excited and focus on our baby, like I planned it to be. But I suffer from anxiety attacks and I have since 2008. So my anxiety really gets to me. I need help, but I don't know what to do. Anyone have helpful advice?