Honestly, it's a really tough spot. Cheating is a betrayal of trust. When your boyfriend called, you were caught in a very bad situation. You need to take some time to think about your actions and why you cheated in the first place. If you decide to talk to your boyfriend, be honest about what happened. He may or may not forgive you, but being truthful is the first step towards resolving this. You also need to be ready to accept the consequences, whether it's a breakup or a long process of rebuilding trust.