What Causes Delayed Periods With Cramping,headaches,insomnia And Bloating?

I am a 46 year old female. My last period was May 1-6 with heavy, normal bleeding. I am a typical 28 day cycle. My next period was due around May 28th, however no period. I had the usual cramping, headaches, insomnia, and bloating before cycle was due, but still no period. Now I am 6 days late, took 3 pregnancy test with negative results. This has never happened before what could be happening? Too old for babies.