What Causes A Delayed Period With Negative Pregnancy Test?

I am on my third pack of loestrin 24fe. My first pack I started my period a week earlier than expected. It was very light and lasted 7 days. My second pack I had some very very light pink and brown bleeding, where it would just wipe away, and it was about a week earlier than my expected period. I didnt get my expected period, so I took a clearblue test when I was 2 days late. It was negative. I've taken 5 tests since then including this morning and all negative. I'm now 9 days late. I've been getting random cramps and headaches, I've also been tired a lot but I get almost 9 hours of sleep a night. My docters nurse( who by the way dont know my name or what pill I'm on or my symptoms) says its normal for the first couple months of starting a pill. Its hard for me to believe her because I've never had this problem with anyother pills. And the last time I was pregnant my only symptom for a long time was my missed period. Am I crazy? Or is something wrong?