Hello, discharge looks brown when it’s discharge tinged with old blood that took longer to come out from your uterus . Brown discharge instead of period could be also the symptom of hormonal imbalance and/or hormonal dysfunctions which women could experience during Polycystic Ovarian Diseases (PCOS), Endometriosis, Ovarian Premature Failure, Hyperprolactinemia and sometimes during use of hormonal contraception including Birth Control Pills.I suggest you to consult gynaecologist considering history of sudden weight gain and no chance of pregnancy.