Your experience sounds particularly upsetting because it seems to have happened little by little. Yet the situation you are in now appears to be a done deal. Your boyfriend is simply trying to have it both ways. He was willing to lose his best friend over this girl and he is now willing to lose you. His lying and unwillingness to even apologize is an arrogant stance that doesn’t bode well for a long-term relationship. A boyfriend who lies, deceives and betrays you then tells you that nothing happened isn’t much of a boyfriend. I wouldn’t invest much more time. Someone who does something he knows will upset you, lies about it, then tells you he didn’t want to upset you is very likely to keep hurting you. It is time to move on.