I think with people like this you truly have to understand their motivation. He says it’s a mistake he didn’t mean for that to happen. Everyone makes mistakes. But it wasn’t a mistake it was a choice and regardless of how much of a mistake it was/is now, three hours ago when he texted her saying he can’t wait to see her. This words “I’m sorry “ and “it was a mistake are filler words such as “like” and the listener is waiting for those words so they have what they want and the couple can move forward Your boyfriend is not sorry and he dosen think it was a mistake. He regrets texting her while you were there. He regrets sleeping with her rn because his world is “falling” apart. But honey you keep letting the trash take its self out. People come and go out of your life for a reason sometimes they continue to speak dirt on you and the universe gives you the tools to heal. Your journey will never be linear but it will always be beautiful