Sydney i advise u to try some other brand of HPT and if it turned out negative then asked ur Dr. for a blood test .do u have some other kind of sympthoms????
It could be a number of things. If your stressed or worrying about alot of things then it could cause you to be late. You could also have endometriosis. Its where u have sist on your ovaries and cause you not to have a period. You need to have a pelvic ultrasound to make sure that it isnt the problem.
Sydney are you having any other symptoms other than a missed period?