hi, i am 23 years old. i have never had sex before except for the usual plays i have with my boyfriend. i have always had a regular menstrual cycle of 28 days until now. i had my last period on the 11th of last month. i havent seen my period this month and i m very worried,i had to use a pregnancy home kit and the result is negative. i had a stomach pain that lasted for a week and i was using buscopan,i also had a tooth extraction. please,what do you think is the matter?