I usually have periods for three months once from my puberty. now i completed 5years from by puberty but it isn't cured.doctor scanned me and say that it is bilateral polysystic ovaries. am i infertile? can't i get pregnant?

Many women with PCOS can and do eventually get pregnant. Many without the disorder have fertility problems and remain childless. You need to work with your treating OBGYN to manage your issues. The pill may be helpful in regulating the timing of menses and you can come off the pill to try for pregnancies. Your future is not defined by this one issue.