Everything has change!

Every since June of 2017, my periods have become irregular. One month the cycle will last 39 the next 37 or even cycle 40 and so many more different numbers and it’s really annoying because I don’t understand why all of a sudden it feels the need to change like this on me. I’m 19 years old not sexually active and works super hard. Could my job be the reason for my periods to have become irregular?