You seem to be suffering from a metropathic cycle this time. It usually happens as one enters the perimenopausal age and as you got other factors ruled out, you may ask your doctor to put you on hormone medication if the situation warrants. The ovaries sometimes need a kickback when they malfunction and the problem gets automatically corrected. Meanwhile try to improve your nutrition, avoid getting anemic and maintain a healthy weight with the Body Mass Index
within the normal range of 19-25. Please get further advice from your doctor. Good luck.