Could Delayed Periods Be Premenopausal Symptoms?

I am 25 years old I had my tubes tied almost four years ago and I have had a reguarl period up until 12/07/2014. Now it has been 61 days late I took test and they came out negative. I also have had my annual yearly test done and all my results came back normal nothing came back abnormal. I still have not had my period. What could this mean.