You can extend your period by taking oral progesterone which is a hormone. Its dose is one tablet three times a day for 10 days starting from the three days before expected days of periods. In case of spotting, double the dose. You will get periods 3-4 days after completion of the treatment. It is not recommended to postponement your period for more than 10 days because if done for longer duration then D and C will be required to induce periods.