Hi Ive Been Taking Pregnacare Tablets For 3 Months Now

Hi ive been taking pregnacare tablets for 3 months now and actively trying to conceive 2 months ago on the last day Of ovulation window I saw light pink spotting through the week till I saw my period then last month nothing and again this month the same thing I came on the period 16th October then on the 29th October I saw light pink spotting until today my period is due on the 12th November. I am concerned why this is happening is it the tablets I am taking ?? Also I gave birth 13th January this year and my periods are always regular 28 days but last month was 26 days.