Suggest Treatment For Brown Vaginal Discharge And Stomach Bloating

18 years old, height: 5ft 4, weight:9stone, clear medical history, one child.
i am taking the microgynon contraceptive pill and im around halfway through a sleave of pills (around 12 days i think) i had unprotected sex around the 25th May at night and forgot to take my pill the next morning on the 27th May. However i carried on taking as normal the day after this. i have never not had my normal break from the pill and always had a regular period. i do regular exercise and a good diet which has not changed recently. the past week i have felt my stomach what feels like bloating alot and the past three days had a brown discharge which do not usually happen. please help, getting confused now.