"As far as effectiveness, this pill works great. I have had unprotected sex with my boyfriend many times and I have never been pregnant.  The periods were light and short- sometimes they were so light it made me nervous that it wasn&#039;t even a real period and that I was pregnant. HOWEVER, my side effects have been bad. I have headaches and especially dizziness. I am in the process of switching.  Overall though the effectiveness of the pill for pregnancy is great."