2 months missed period!

Gabrielle

Hello I am 26yrs old and I have been tracking my period for the last 7 plus years and have been pretty regular. I will usually get my period between 28-30 days. The past 2 months I have missed my period. 8 test later and a blood test ruled out pregnancy. No change in diet, exercise, or medication and I have not been on birth control. I have felt absolutely normal. What could be going on??