I have fallen in love with a married man. What should I do?

Keep your boundaries at once and, if it is serious, take the lawful route — a formal proposal to the wali (guardian), not a secret relationship. The feeling itself may be unavoidable, but exchanging affectionate messages, meeting alone or carrying on a secret relationship is forbidden and wrongs his wife and family. Ask yourself: is he able to be fair? Is he honest with his wife? If the answers are doubtful, it is better to step away. Pray istikharah and seek your family's advice. If he is serious, he will come to propose through your wali and follow the procedure.