My period is now going on two months late, what could be the problem? I've taken two test they both came out negative, as well as I went to a clinic and those results were negative.

Many causes inc PCOS. A one-off late period can be caused by stress or an ovarian cyst. Irregular cycles can be due to polycystic ovarian sydrome (pcos), also thyroid problems, excess prolactin hormone, aging of the ovary (diminished ovarian reserve), or low hormone levels (hypogonadism) from heavy exercise, eating disorders, or stress. Some medications can affect your cycles. See an ob/gyn, or a rei specialist if ttc.