How To Deal With PCOS?

hi i have pcos but for the last 7 months my periods have been on time gve a few day before and after my due date but now i have not been on since the 14th march iam also trying for a baby with my fiance i have done a few pregnancy tests and all have said no.But for the past few weeks i have been getting really bad stomach cramps,feeling sick,crying alot at anything but really moody also,not sleeping,sore breast and bad back at he bottom what can all this mean is there anyway that a pregnancy test can not pick up the pregnancy hormone i read a woman didnt show up pregnant until she was 9 weeks gone can this be right?