1. test done to detect pregnancy
should be done after 10 days, when zygote
is formed forming an outer layer of Trophoblast
which secrete hCG around 14th day.
2. prior to it, either implantation
is not there or the body is not producing enough hCG to be detected in pregnancy test.
3. if pregnancy is not +ve then other causes can be STRESS, rapid gain or loss of weight, recent change in diet.or use of birth control methods.
4. unless you're pregnant,chances are her cycle will return to normal next month.