Since you are a case of PCOS, irregularity in your menses is cofusing you more. I do not think, every missing period should be suspected for pregnancy. Once your menstrual cycles are regularized then you think of getting pregnancy test done after a missed period. The helpful pregnancy tests are HCG levels - quantitative which is very costly and qualitative which is quite cheap and can be done at home. These tsts are of different types. Some tests which see beta HCG are very sensitive and can show positive results even just 2 days after missed period. However, the common tests become positive after about 8-10 days after missed period. Accordingly you may plan your pregnancy testing. The other way is to get ultrasonography done. It can be done transvaginally of transabdominally. The first route give the results earlier than the abdominal route. Abdominally, the rest shows reliable results around 8-10 days after the missed period. Getting clinically examined from en Obstetrician 2 weeks after a missed period is also a good option. I have informed you the list of the tests and when to do them Accordingly you can choose the test and plan the timing. However, I feel till you get your mesnses regularized, please do not get excieted after every delayed period. Hope this takes out your stress and guides you properly.