What Does Missed Periods And Pregnancy Test Report Indicate?

Hi I have missed 2 cycles of my period. I went to the Dr. and we did a pregnancy test, it was negative. The only thing that i can think of that my have effected my cycle is that I started taking Hydroxycut diet pills in January 2015. I missed Feb and March periods. I stopped using the pills since March 15th. Would these specific diet pills ( hyroxycut ) have anything to do with missed periods?.