A menstrual ycle that lasts more than 5 months is definitely not normal. Longer cycles mean rarer menstruation (oligomenorrhea) and rarer ovulations. Chances for conception are smaller the less frequently you ovulate.
Oligomenorrhea could be a sign of hypogonadism. Hypogonadism is a condition wherein the function of the axis ovaries-pituitary-hypothalamus decreases. Depending upon the localization, hypogonadism can be primary (ovaries), secondary (pituitary gland) and/or tertian (hypothalamus). You may need to check some of your blood hormone levels: estrogen, progesterone, testosterone, FSH, LH, prolactin, thyroxin. You can consult a gynecologist who specializes in endocrine disorders about this.