Your
beta hCG of less than 0.1, done 37 days after intercourse, rules out pregnancy. You don't need to repeat it. The delay itself is very likely from the emergency contraceptive pill, which commonly pushes your next period off by days to weeks on its own.
Next Steps
You can wait a little longer for your period to come naturally. If it still hasn't started 7 to 10 days from now, see your gynaecologist to discuss whether Meprate is right for you instead of starting it on your own.
Health Tips
See a doctor sooner if you get heavy bleeding, severe pain, or your period still hasn't come after another 2 weeks.