Hormones are a real pain, aren't they? This can happen, periods just don't show up and we have a really long cycle but STILL have the PMS symptoms. Grrr. Try not to worry. If you don't have it for 3 straight months, call your doctor as they usually want to see you around that time frame. I had a slow thyroid and had periods about once every three or four months for a year and a half in my 20's. It righted itself. Use good protection because you don't know when you'll next ovulate--- just in case you decide to have sex. But generally, this can happen and is not a big concern. good luck