Do You Have to Tell?

Do you have to tell the person you are having casual sex with that you are now in a relationship?

Is it any of his/her business?

Do you ignore the texts and phone calls?

If you do respond to the texts and the phone calls, do you make up excuses as to why you can't come through, hoping that he/she will get the hint that y'all cannot hook up anymore and stop hitting you up?

Or do you just come clean and tell him/her the truth?