If you think what you did was not right, then you are feeling guilty. And cheating is often defined by the person. You didn't kiss him, you didn't sleep with him, but you were practicing your flirtation and teasing with him. Think of it this way, if your boyfriend did what you did, would you consider it cheating? Use that as your guidepost.
However, even if you consider it to be cheating, do you think it would be wise to tell your boyfriend? Nothing good could come of that and you seem to know that it was wrong and won't do it again, so it could just remain between you and your friend. But seriously ask yourself why you allowed yourself to do it. Maybe there is something missing your relationship that you didn't even realize.
Good luck.
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