Yeah I'm on the same boat here. Im over 2 weeks late and this has never ever happened to me before, I was always very regular, but I keep getting negative results. So I would tell you to go to the doctor and ask for a quantitative HCG test because that is the most accurate test you can take.
the best thing for you to do is get a blood test.from experience, a missed period doesnt always mean pregnancy,even though we want it to.lol.in november i missed my period all together,it never came. i did test after test and all were negative.i was sooo confused because just like you,my periods were like clock work.so words of encouragement go to the docs asap.your hcg level may not be detectable.so good luck sweetie