Were you prescribed anything for your teeth and, if so, did you use another form of contraception?
Stress can be a major factor in stopping periods/making them irregular but if you are still worried about the possibility of pregnancy you can ask your doctor, if they think it's necessary, for a blood test to determine possible pregnancy.
Saying that, personally it took around 4 or 5 months before my periods stopped when I first started taking micronor (pop) and I wasn't pregnant (that time - not scaring you hun)
Best of luck with it.