Can I be pregnant. Hcg tests reliable?

Mam i had my periods from 2nd feb to 6th feb, i was on ovral l from 3rd feb, taking every night at 11 pm, had sex using withdrawal method on 9th feb-as in i had taken 6 pills by that time, took unwanted 72 within 5 hours, and also took the 7th pill that day, and continued taking the pills. my expected date of periods was 2nd march. i took a beta hcg test on 1st march, 8th march and 15th march all values less than 2 iu/l any chance of pregnancy? if i was pregnant, the beta hcg value would have been greater than 2 iu/l by 8th mrach right? were the tests taken in  accurate time to detect pregnancy if present also are beta hcg tests reliable? im very scared 1st march was 19 days after intercourse, 8th march 27 days after intercourse and 15th march was 34 days after intercourse, if i was pregnant, it would g lmp on 2nd feb, 8th march was 34 days past lmp and 15th march was 42 days past lmp on 2nd feb