It’s common to not have it due to malnutrition and/or extreme stress.

My grandmother was an army nurse during WWII (European front/combat/dragging wounded soldiers from the field kind of nursing), she said most nurses either didn’t have periods at all or had them very on and off (on and off was more common).

She once didn’t have it for the entire year, then it came back full speed in extremely uncomfortable situation (on the train with no supplies or accommodations).

Human body is so confusing. I’d say yes malnutrition causes disruption in a cycle but it doesn’t mean it can’t come back. Yours seems to be back for the time being but it’s not the same in terms of amount of blood