I was wanting to know what are the chances of me being pregnant? I am a week late, took a test 3 days ago and it was negative, and oh by the way I am 51 yrs old. Help.

Odds are far greater it has to do with menopause. While it is not unheard of to have a "late in life" pregnancy happen naturally (and some women are just naturally fertile for a longer period of time), fertility starts to decline sharply once you get into the mid-fortys.
Give it another week, and if still no period, try another test. If still negative, see what happens the next month. Schedule a visit with your doctor if still no period at that time.