AIO. I found this text from my boyfriend to his coworker

I (29F) found this text in my bf(29M) messages with his coworker. I’m feeling a little gutted from it. I don’t want to overreact, but I also don’t want to gas light myself and under react. I haven’t once felt this way about him in our relationship, so I’m feeling really taken off guard here. How do I go about this?