I use Alexa for 4 months and in this pause did the menstruation delay?

I used the contraceptive Alexa 4 months ago, in this last 24-day card, instead of the fifth day I took it again on the seventh day, I had eight relationships during this month without condom use, just relying on the pill. After the end until today the menstruation did not descend (4 days). Should I go back to take another pack on the fifth (tomorrow) day? Am I at risk of being pregnant? I have some abdominal cramps but no sign of the cycle. Should I be worried?