If you have missed your period by 26 days and your pregnancy test is negative, there could be several reasons for your symptoms. One possibility is hormonal imbalances, which can cause changes in your menstrual cycle and lead to symptoms like breast tenderness, white discharge, and cramping. Other potential causes include stress, excessive exercise, changes in weight or diet, or underlying medical conditions such as polycystic ovary syndrome (PCOS) or thyroid disorders. It's best to consult with a healthcare professional to determine the exact cause of your symptoms and get appropriate treatment if needed. They may recommend further tests or examinations to rule out any underlying conditions and provide you with personalized advice based on your specific situation.