Hi, and thanks for your medical question on eHealth forum
The periods may be missed or their pattern altered while on Seaonique. The other possibility is that you missed some pills or there was an irregular intake with the cycle getting delayed. There is a chance of pregnancy too.
Wait for the complete pack to be over and if you still do not get your periods then repeat the pregnancy test.
If it continues to be negative, consult your gynecologist to rule out other causes like hypothyroidism, PCOS, anemia, etc. Hope this helps. Take care!