What Causes Soreness In Breast,lower Back And Headaches?

Hi, I am Charmain. I have been sterilized 4 years ago. I done a preganancy test yesterday and it showed negative. So please advice and tell me what this couls be. For the past 3 week my breasts are very sore. On Saterday i had a dark brown discharge and yesterday again. This morning when i woke up my lower back is so sore and the pains don't go away. I get headaches which last for 10 mins and go away again. Could this be stress?