acts by avoiding ovulation.You had stopped the drug half way the second course. Normally this should follow a withdrawal bleeding, which you never had.
There is another possibility, of ovulation being recovered after withdrawal,You have history of regular sex in between. So possibility of late conception can not be ruled out. The pregnancy
test you had done,might be too early to detect.
Please get your Blood HCG
test done after a week more.( If there is no pregnancy, you may get late withdrawal bleeding )
scan may help .
Consult a Gynecologist for guidance & advice.