Sometimes this can happen and if he's been good since then I wouldn't worry. However, because you are asking the question it appears you have a gut instinct he's up to his old tricks. I believe in listening to gut instincts. Once a person cheats on another there is a trust issue and the relationship seldom will last the test of time.
They both are bad. If your best friend cheats on you with your boyfriend, she is a NOT a loyal friend. And if your boyfriend cheats on you, DUMP HIM.
Are you physic?
dump him
yes but she cheats on him.
Ask him.
You torture him.
YES
shoot him in the head
it's still cheating.
Time to say goodby to your boyfriend and probably your bff, too. Why would she go out with your boyfriend if she was your best friend?
fool me once, shame on you. fool me twice, shame on me.
It means he doesn't really care about you