Hi,
Thanks for posting in HCM.
I understand your concern.
Experiencing brownish urine or having abdominal cramps does not indicate that you are pregnant. Pregnancy could only be suspected when you miss your periods and that could be confirmed by means of urine pregnancy test.
However, you still seem to have time to take emergency contraceptive pill to prevent pregnancy. It needs to be taken within 72 hours after an unprotected intercourse to prevent pregnancy. Earlier it is taken, the protection seems to work better. You can take it once you are back as it is available in any pharmacy over-the-counter.
It protects from pregnancy by causing withdrawal bleeding within 3 weeks from the day of intake of pill. In case this doesn't happen, you need to seek medical attention immediately.
Hope the information provided would be helpful.
All the best.

Thanks for asking at Healthcare Magic. I read your question and I understand your concern.
The average duration of pills effect is 1-4 days.
Ovum after ovulation remains for 72 hours in fallopian tube. Fertilization of egg (ovum) by sperm occurs in 12-24 hours.
Hence all these three factors should be taken into account. If you are in ovulation phase and you have not taken pill yesterday then chances are more. If you have taken pill yesterday and not in ovulation phase then chances are minimal.
But at the moment these are not signs of pregnancy which you have mentioned. Only pregnancy test become positive after 8 days and signs symptoms start to appear after 14 days to one month. Hence you are not pregnant.
All that you have to do is to take two pills tonight when you reach home.
Hope it helps best.
Take your best care.
Don't forget to rate this answer and close the discussion at Healthcare magic.
Regards
Dr Ejaz