What should you do if you are cheating with your best friend's boyfriend?

You would not like it if your best friend cheated on you with your boyfriend so that is not a nice thing to do to your best friend.

First, you should stop saying you are best friends with the girl when you are

'cheating" with her boyfriend. Best friends do not do that. Second, you should stop going out with her boyfriend. Third, you should tell the girl that the guy is cheating on her, even though you will need to tell her that it is with you. If he does it with you, there is a real good chance that he would cheat on her with someone else. Finally, both of you should dump the guy.