medium to long distance running

Question
I have bumped my long run mileage up to 8-10 miles and 2 out of the three times that I havew run it, I get extremely nautious within about 15 minutes after I finish and it lasts for 3-5 hours.  The first time it happened I would sweat profusly and shake some but this last time I juse experienced the nautiousness.  What could be causing this.  I don't think it's dehydration as I usually experience a headache when I have dehydrated in the past.  

Answer
marie
you have to give me more info on your training and your self before i can make assesment.things such as age height..weight..how long running..mileage per week..pace your running on long run and what efort heart rate etc.is your long run at 65..70..80..85..90..pesent of max.aprox.and what did you bump your long run up from.
get back to me marie
the best to you
John DeHart
rentacoachinternational
albuquerque new mexico
www.howtobefit.com/howtorun.htm