Backache and breast pain in ladies can be due to pregnancy. Other possible reasons can be premenstrual syndrome (PMS) and use of some hormonal medicines like birth control pills. High progesterone levels during pregnancy cause these symptoms. Progesterone levels are also high few days before periods and mislead for pregnancy. Many other condition can cause breast tenderness and backache. You should get pregnancy test if you have missed your periods. If the test is negative then visit a doctor for proper diagnosis and treatment.