You did say you had blood work, were you told of any other health issues? Are you unusually thin or possibly not eating enough? Could you be anemic or have thyroid problems? Are you under an unusual amount of stress? All of these things affect women's cycles.
I often went over a year when I was young with no period. My gynecologist told me I possibly had what he termed "refractory" ovaries. Whatever he meant...
eventually my periods started to become regular, it's hard for me to know what did it. Nature, or maybe better nutrition? To this day I don't know.
