Missed period, but negative HPT's. Advice?

Sometimes, because of stress or other factors, women will not ovulate when they typically do and this will result in a longer cycle. Even if every cycle you've ever had was 27-29 days, you can still get a longer one every once in a while. Charting your cycles will give you a better understanding of this, check out fertilityfriend.com. For this cycle, my advice would be to test once a week until you either get a positive or your period shows. If you go 60 days with no period or positive test, then call your doctor. Good luck!