Need quick opinions and advice.

I began my first period at 9 years old (early I know LOL) and I am 20 now. It's always been pretty consistent with coming on the same week.

Recently, it has been weird. It didn't show in April at all, May 12th it showed, and now it's showing signs this week (June 20s). I have been stressed but this is not common for me. I am not sexually active , still a virgin.

Any thoughts as to why it is so inconsistent with dates ? Thank you.