rapid loss of distance vision

I am starting to get really worried.  I have never had any eye problems until I started university.  I went to get my eyes checked when I was 20 to discover that I had -0.5 and -0.75 prescription.  Since then my long distance eyesight has been dropping non-stop.  Every 6 mths or so I find that I need to change my rx... i am now 26 and my rx is -3.5 and -4.0!!  I'm scared that at this rate I will become legally blind by the time I'm 30!  
I have no medical problems and should also mention that absolutely noone in my immediate or extended family has any eyesight problems!  My eye doc checks my eyes every year and says that I don't have any eye diseases and that my eyesight is worsening because of stress or because I wear contacts too much!  Seriously??  It is true that I end up wearing contacts for about 12 hours a day, because I hate wearing glasses and find that contacts are a lot more convenient.  But I have so many friends who do the same and their eyesight is the same as when they were 6 years old!
I've changed the brand of contacts a few times, and have been wearing "Night & Day" for about 2 years now...   Even though the package says that you can wear them for 30 days nonstop, I always take them off for the night.   The result is the same, my vision keeps decreasing. I don't understand!!

[harvhealth]

hi friend
i have the same problem in my right eye it started exactly like your's some 5 years ago at the age of 24. your post is quite old did you get the answer of your problem?

[John C Hagan III, MD, FACS, FAAO]

1. Stress does not cause myopia or needing glasses
2. Your eye is likely very healthy only just too long for the internal focus muscle and corneal curvature. You have 'adult onset myopia"  so do I as I started to need glasses midway through medical school. You are not likely to become highly myopic.
3. Your contacts are NOT a factor.
4. See an Eye MD and discuss lasik if you don't like glasses or contacts.

JCH II MD