hello and thanks for the query,
well considering your history and your LMP date you have missed your periods since your urine pregnancy
test has come back positive which is due to raised beta Hcg
levels and it would be better if you got a repeat USG after a few days and the brown discharge could be due to an ectopic pregnancy so I would advise you to get a blood levels of Beta HCG also. Your gynaecology would guide you regarding the management of the situation .