Sounds to me like BF % may be a bit low, BUT.... I haven't had a cycle since Novemeber of 2000. I have had cervical cancer, and god knows I have "issues" but there is no real reason that anyone can give me as to why I don't get a period?? According to my blood tests I haven't gone into menopause, and I despite the bout with cancer I still have all my vital parts- so go figure??!
I would say - go to the doc! If it is BF %, you want to be sure and address that.