Women with PCOS may commonly experience low back pain, sacral pain, and lower quadrant abdominal pain and you need not feel that you are pregnant simply based on that. To become pregnant you would have to have unprotected sex between the 10th and 18th day of your cycle. If that is not the case and if your pregnancy test is negative, you need not worry. The pain in PCOS is generally due to the bursting of the follicles within the ovary in order to release the ovum. It can also have a component of muscle spasm associated alongwith.