As you had intercourse one week after the period, it may not have fallen inside the fertile period. Also, since you took the emergency pill, you are safe. The reason for your last scanty period should be known. Gaseous distension of the abdomen is part of the premenstrual state. You can wait for a week before you take a pregnancy
test, preferably a blood test
. I advice you to consult a gynecologist if you do not a cycle and get evaluated for proper management; your cycle may get delayed as you have taken the pill. Take care.