An extended period of time where the menstrual period is absent and there is not a current pregnancy is often a sign of infrequent or absent ovulation. If you had previously had normal periods or had somewhat unpredictable periods, I recommend you have an evaluation by a Gynecologist.
A period is initiated by the cessation of progesterone production approximately 14 days after ovulation if a conception has not occurred. This production of progesterone by what is called the corpus luteum only occurs if you ovulate, therefore it is common for women to go long periods of time without menstruation if they are not ovulating or ovulation infrequently. If you are not ovulating, the bleeding that will finally occur is because of instability of the lining of the uterus due to being continuously stimulated by ovarian estrogen without the counter-balancing effect of progesterone that comes after ovulation. This can not only make it difficult to conceive, but prolonged overstimulation of the lining of the uterus by unopposed estrogen can increase your risk of uterine hemorrhage, endometrial hyperplasia as well as uterine cancer.
There are many risk factors for absent or infrequent ovulation such as obesity, smoking, diabetes, family history of infertility as well as a common condition called Polycystic Ovarian Syndrome. Women with these symptoms should be evaluated whether they are currently seeking pregnancy or not given the complications of having these conditions and not being treated.
There are many explanations for what you are going through as well as readily-available treatments for these conditions both for women who are trying to conceive as well as women who do not desire current pregnancy. I would recommend visiting an OB/Gyn to discuss this further.