TTC and now this curve ball

My husband and I have been TTC for 5 months, tracking my period and ovulation. I have always had a normal cycle, before and after any birth control. Well now I'm 2 weeks late and have been taking preg tests every 3 days or so and still negative but no AF.

I have never had this problem. Why no period but no BFP?? I called my doctor and she said 'give it a few more days' .. but wouldn't this indicate a problem? I don't have any symptoms but I am so confused.

What should I do? What should I be concerned about?