Hello,
Although pregnancy is the most common cause of delayed periods,but no. of other causes can be there.You can confirm your pregnancy by home based UPT test which measures HCG in urine by as early as 11–14 days after ovulation.However false negative results are also common.So the best way to confirm pregnancy is by ultrasound uterus.
Other causes of delayed periods are stress and anxiety,eating disorders,too much exercising,hypothyroidism,chronic illnesses,PCOS(polycystic ovarian syndrome) and in rare cases,tumors of the pituitary.
I feel that an evaluation by a gynecologist and ultrasound uterus,thyroid evaluation and hormone studies will be the best.
Hope it helps.Take care and pls do keep me posted on how you are doing.
Are you sexually active and/or on birth control? It's not uncommon for periods to be "irregular" once or even twice a year, but usually this irregularity wouldn't be more than a few days to a week overdue.
Have you been stressed recently? This could have caused your period to be late in the first place and then the fact that you've probably worried about it since it was late could only be adding to the problem.
Home pregnancy tests are only accurate as early as 1 - 3 weeks following conception (depending on which pregnancy test you took). False negatives are possible, as are false positives, but I would definitely recommend visiting a gynecologist as soon as possible--if you're sexually active or you're at least 20 years of age, it's generally good practice to visit a gynecologist at least once a year, regardless of whether or not anything is wrong.