What Causes Delayed Period, Brown Vaginal Discharge And Breasts Soreness?

Hii am Prashanthi,my age is 25.i have one son of 4 years old.now again from 2 years trying for baby.in this month my mensus we re stopped.actually my last period is on 19th jan .so did serum pregnancy test on 26th February it s came as =25miu/ml negative. Then again I did SPT on 2nd march it is also negative.then doc gave me duphaston 10mg daily 3tab for 5 days.on first day after using duphaston little brown discharge is there ,it is like white discharge n little bit a blood. And also it s paining at the lower abdomen,back pain....,breasts r sore from 1 month.