Thanks for the query.
The chances of pregnancy
are less in your case unless there was few spermatozoa
in premature ejaculate and your intercourse occurred around the time of your ovulation.
According to your description your symptoms could more possibly due to the side effects of the emergency pills.
Emergency pills should not be used frequently, as they can lead to side effects like menstrual irregularities, pain abdomen, bloating
For more details:http://srsree.blogspot.in/2012/08/emergency-contraceptive-pill-short-term.html