Does Norethisterone Affect Pregnancy Test Results?

Hello sir, I am 21 years ( unmarried ). I usually have my period on 19th or 20th of every month. I missed my period in the month of May ( not because of sexual intercourse ). I had unprotected sex on the 6th of June and missed my period again in June. 17 days after intercourse (23rd June) : Both home pregnancy test and BETA HCG test were negative. 20 days after intercourse (26th June) : BETA HCG came back negative. I have no symptoms of pregnancy like nausea, cramps, white discharge etc. I could not tell my mom about the sex issue and as she was worried about my health due to my missed period , she took me to a gynaecologist , who asked me to take NORETHINDRONE ACETATE ( 5 mg ) tablets for 10 days. I started the course on 22nd June. Please let me know : 1) If norethindrone acetate tablets can reduce levels of HCG and cause a false negative. If yes, then how must i take a pregnancy test . I cannot stop the course ( My mom would not let me ) 2) If i can still be pregnant after a beta hcg test (as late as 20 days after the intercourse) 3) If i should repeat the test . Please let me know beacuse i am really worried . Will always be thankful .