The pill is pretty effective UNLESS you are taking other meds that might make the pill less effective (Antibiotics) so there is a very small chance that you can get pregnant on the pill..... BUT if you have taken no antibiotics and have not forgotten any pills you should be fine
Some birth control acutally similates pregnancy. I was on depoprivera last year and I thought I was pregnant severaly times. Sore and swollen breats, etc... but, the tests always came back negative. After I did some research I found that the birth control was actually causing the symptoms. Maybe this is the case with seasonique, although I have never heard of the pill.