Delayed period. What must be the reason.

I use to get my periods every month on time. I use to use the clue app to track my periods and it use to be accurate. But this month I did not get my period yet. Last month I got it by 1st September and lasted for 4 days. I use menstrual cup since a year and more. My periods never got delayed since past 3 years. But I did not get it this month .I wasn't active sexually since past 9 months, I use to use maftal spas tablet on the 1st day of my period as I had extremely unbearable period cramps, apart from that I did not consume any medication. Every night I consume 2 capsules or organic India ashwagandha and some days when I workout I take one scoop of iso pure whey protein powder with water. Nothing more then this.. what must be the reason.. I am seriously worried