What Causes Prolonged Vaginal Spotting?

Hi doctor I had my last period on February 6th. Usually my cycle is 25 days. From March 5th I m having the pain. On 6th I saw 1 drop of blood when wiping. And on 7th night I had some bleeding.. Now again I m not having anything. I m married, but I m using contraceptives.. And before 5 days I had palaya juice and pineapple pudding.. If I m conceive will it effect that.. Can I know what s the reason of this drop by drop bleeding then??