Does anyone know how fast this disease progresses without a proper diagnosis

Please go to this link:http://www.alz.org/alzheimers_disease_stages_of_alzheimers.asp

It will list the stages of alzheimers.
Most individuals with alzheimers/or dementia will be in a combination of 3 stages with the middle the most current stage.
Wether diagnosed or not, the course of alzheimers seems to be individual.
By the time you notice significant symptoms it has progressed much farther than you think.
With proper health, diet, activity, and sleep it can progress very slow.
Yet is some extreme cases it can move in a manner of 2-3 years to end of life.

Getting a proper diagnosis is not always easy w/AD. It is very vague and hard to be sure except for a brain exam at autopsy. Whether or not you have a proper diagnosis will have nothing to do w/how fast it progresses. As already stated, read about the stages and you are probably further along than you realize. As for time--maybe one yr after diagnosis, maybe 12, maybe 20. No one knows. The average length of life after diagnosis is 7 yrs, but it varies greatly.

The web site below will also help you to understand a little more about the disease.