Change in period length

I have been using the same period tracker for 8 years and sometimes that bitch knows my cycle better than me lol. After 8 years, I have a 77% regularity rate and an average cycle length of 27 days. Last month, I was 4 days late, making my cycle 31 days. The only other times I was that late was with my pregnancies (one full term, one miscarriage). So, to say last month was devastating when I started is an understatement and I am currently three days late.

Has anyone else’s cycle suddenly changed like this? I know stress, illness and other factors can cause you to be late, but two consecutive months? I mean last month I was on freaking vacation and was late lol. Thanks ladies!