I am afraid of the future and of my place in the family after my husband takes another wife. How do I calm this fear?

Fear about the future is usually bigger in the mind than in reality, so separate what is certain from what is only imagined. Write down your worries one by one: finances, love, the children's position. Then ask your husband about the things that can be clarified, such as guarantees of maintenance (nafkah) and the rota, so that some of the fear eases with certainty. For financial and property rights, you can discuss openly and, if necessary, refer to officers at the religious affairs office. Entrust what is beyond your control to Allah through prayer and tawakkul (reliance on Him). Build your own support: knowledge, skills and a social network. The future becomes less frightening when you are prepared, not merely imagining the worst. See existing wife.