Am I overreacting?

My husband and I have been married for almost a year now and we are expecting. The other day I was going through his phone to see how often my family helped him when I was stationed overseas( I’m in the military) and I came across a message from an employee of his. I read through the messages and came across some messages where they both said they loved each other and got a pit in my stomach. This was said when I was still overseas. He says that they are only friends and that she was just saying thank you for him helping her. Am I overreacting?