I don't have experience with that medication, but I know stress sometimes makes periods late or skipped altogether.

I've been on vyvanse since November 2022 my periods are very much regular still. Maybe starts a day earlier some months but have never missed one. Only problem they cause me is constipation which is really annoying, uncomfortable and painful. Have you been to your doctor and had bloodtests to see if its to do with your thyroid or any other undelying conditions ?