Hi thanks for your question.
Due date for your cycle was 16 march and you are over due only by 6 days.Pregnancy
test turns out positive 10 days after missed periods and you have got your pregnancy test done little too early.Repeat pregnancy 10 days after missed periods to confirm or rule out pregnancy .The bleeding on 12th of march could be implantation
bleeding (bleeding which occur during implatation of fertalized ovum?into uterus
Hope this answers your question0