Period 3mths late had neg preg test until today that says 5weeks +. why has it taken so long to get pos result? lots of low cramping normal?

Cramping abnormal: If you are having cramping pain after 3 months of missed periods, and with a positive pregnancy test, there are 2 main concerns: cramping pain can be a sign of miscarriage (spontaneous abortion). Another possibility is that a tubal pregnancy (ectopic pregnancy) can cause pain at this time - and it's potentially very dangerous. Please see your doctor to find out for sure.