Hi thanks for your question.Pregnancy
test turns positive 7 to 10 days after missed periods. You got your 3 pregnancy test done 2 weeks after missed periods. All were negative. Your serum test was also negative. There are various reasons for delayed periods and hormonal
imbalance is the commonest cause. Anxiety (tension) is anther common cause. Chances of pregnancy are very less but to be 100% sure you’re not pregnant ,rule out pregnancy by ultrasound
as you have again started BCP .Taking BCP in presence of pregnancy is dangerous..Birth control pills can produce vaginal discharge
which can become bloody due to vaginal infection
Hope this answers your question.