Should you tell your boyfriend of a month about a one night stand?

Answer 1

If it was before you began your relaationship, no. There's no point and it's completely irrelevant in any case.

If it was after beginning your relationship, you might want to tell him. He hears it from you first and you don't start a habit of cheating on him.

Answer 2

You should do whatever you think is right. Although honesty is the best answer (and believe me, i know) you shouldn't let people talk you into something your uncomfortable with. If your nervous about telling him, wait a while until you are ready.