Are Stomach Pain, Headaches, And Effects On Mental Health Side Effects From Sevista?

i have been taking sevista 30 alternate days as prescribed by my doctor for the pain in my breast and i do have a lump . I feel that because of the medicine im having side effects like stomach pain headaches and even mentally it’s affecting. Is it normal for all these things to happen i have took it for 2 months 1 more month is left