My boyfriend made me promise not to tell my friend her boyfriend is cheating

my boyfriend told me my best friends boyfriend had sex with another girl. he made me promise not to tell her! what do I do? its killing me!!

Your boyfriend is being immoral. Tell your friend. If your boyfriend cheated on you and your friend knew, wouldn't you want her to tell you? No girl should be treated like that. and if he wants you to not tell perhaps he plans on cheating himself. I would talk to your boyfriend and tell him that you can't watch your friend get hurt. You may have some loyalty to him but it does NOT justify hurting someone or allowing someone to be hurt.

stick with your friends

Never choose a boyfriend over your friends!