How do I deal with the pitying looks or whispers of people around me after my husband takes another wife?

You owe no one an explanation, and other people's views do not determine your worth or your happiness. Some of the sympathy is sincere, some is mere curiosity; you can choose not to entertain either. Prepare one short, dignified answer for nosy questions, for example: ‘Thank you for asking, that is our family's matter.’ Avoid giving details to people who have no need to know. Surround yourself with people who support you, not those who add drama. Focus on your own life, because people's gossip will soon move on to another story. Calm dignity answers better than any defence. See mental health.