You had sexual intercourse at the crucial time (around ovulation), are having nausea
and one of the pregnancy
test is positive, so there is very high likelihood that you are pregnant. The nausea as a side effect of metronidazole
is usually not so severe. Another possible cause of nausea may be vaginosis but again that has to be really severe to cause such nausea. Now next option is to wait and watch or repeat a urine test the third time and the go to gynecologist.