Welcome to HCM,
You are young you have not mentioned that did you have any sex or not ,if yes then your pregnancy
test is positive and you should consult a Gynecologist and you can repeat the test and after examination a blood test
of Beta HCG and Ultrasonography
will guide line of treatment.
Other possible causes may be following.
A)Test within 2-5 minutes (or whatever the manufacturer recommends) and disregard any results that appear after this time
B)Pregnancy tests may display a false-positive result when moisture crosses the test.
C)Expiration date or has been exposed to extreme hot or cold, disregard the results.
D)Molar pregnancy, or Ectopic pregnancy.
As your period is irregular please consult a good Gynecologist.
Other wise delayed period could be due to
,Miscalculation,Change in Schedules,Hormone Imbalances.
Please take care