I Have Been Advised To Take Duphaston 10mg For 10

I have been advised to take duphaston 10mg for 10 days starting from 17th to 26th day of the cycle for conceiving. My periods are delayed by 5 days accompanied with severe lower abdominal pain which lasts for a few minutes for the last 5 days. Home pregnancy test gave a negative result. Is it normal to have the pain? Does this medicine delay periods? I had a history of endometriosis but there are no cysts for the last 1 yr. My cycle is normal. please advice. Thanx