I have gone through your query and understood your concern. Whenever there is a delayed period, in addition to exclusion of pregnancy
through a HPT or blood test
if you are sexually active, a trans-vaginal/pelvic sonogram also must be performed to know the status of the pelvic organs. This also helps to exclude/confirm pregnancy and also to know the thickness of the endometrium which in turn helps to assess the amount of blood loss to be expected in your next period. Since you have used a combination medication, you should wait for 3-7 days to see a period and if you do not attain withdrawal bleeding even after ten days, get further help from an expert. If the bleeding is heavy, you can control it with styptics and if needed, with a course of hormones. Hope this helps.