Ovulation without menstruation occurs only if there has been conception after ovulation. If there has been no conception, ovulation is always followed by menstruation. It is possible to have regular menstruations without ovulation; these are not a real menstruations but are called "false" or "pseudo-menstruations". It sounds as if you are suffering from hypogonadism. This disorder causes a lack of ovulation and manifests itself by withholding menstruation (amenorrhea). Hypogonadism can be classed as Primary (disorder of the ovaries), Secondary (disorder fo the pituitary gland) orThertial (disord of the hypothalamus). A hormonal analyses (FSH, LH, Gn-RH, estrogen, progesterone, prolactin, testosterone, DHEA) have to be done to locate the origin of the problem.