You should bleed before the next packet. most probably, there is very less chance of not geting periods in between. it can stop or make menses irregular after you stop taking it. Now let us assume that you don t get periods in between which is less likely than you can look for these early pregnancy signs, Nausea and vomiting more frequent and more in the morning (Morning Sickness) Feeling of weakness Feeling of evening raise of temprature increase urinary frequency in some case more constipation without any reason More frequent vertigo episode Out of which Nausea and vomiting is the first and on which you can rely somewhat more as a screening for failure of contraception and pregnancy.