Will Primolut N Protect Me From Pregnancies?

i`m singl and my mencies should be after28-32 days but i`m now 33 days it`s not come and that first time happened with me since 22years my menarch was 12 years old and i`m afried to get pregnant from my boy friend.Is primolut n will not allow to be there any chance for pregnancy? Or there is any madication do that please tell me and what is the does and said effect of me?