Hi I am 46 and have not had my period for 2 weeks. I was very regular befre. I did preganancy test it was negative. What could be the reason?

You could be experiencing the beginning of menapause. Have you had hot flashes or night sweats?

No I have not

I would give your doctor a call. If it is menapause you may need to get on some sort of hormone therapy or some supplements.
My sister, who is 36, is currently in pre-menapause and is having to take a calcium supplement and estroven. She is only suffering from night sweats right now and really bad mood swings.
Good Luck.