What should boyfriends and female colleagues do if they send text messages every day?

What does your boyfriend talk to her about? Are you sure they are talking? You should pay attention to how much she cares about you. You can feel whether she cares about you, right? If he is kind to you, you should trust him. I can tell you a way to know if he betrayed you. Go to his office and see if he will introduce you to his friends. If so, you are asking his friends (of course, you must know them well). If he can do it, that's your problem!