How Can Irregular And Delayed Periods Be Treated?

hi i usually have irregular periods . my last period happened on 26th nov. i had intercourse in the last week on dec. i have not yet got my periods. from jan 16th to 18th , i took deviry twice a day to prepone my period but still havent got it . what does this indicate and what best can be done ? am i pregnant ? if,so , i do not wish to concieve now .. pls suggest.