My wife has her period every three months. Her one sister also has the same situation.
She used to take the pill to regulate her cycle monthly (prescribed by her doctor). My wife has struggled with her weight most of her life.
When she started training for a half a marathon, she lost some weight plus the regular fitness speeded her cycle to every other month.
I would not worry about it. Go see your family doctor to talk about it.
Hope this helps,
tomz