Water Logged

I have been trying to loose weight for some time now. I am working on a very specific program with a lady I know. We have been keeping track of what we eat and drink every day. After three weeks she told me I wasn't drinking enough. I usually have 2 large glasses of water a day, max. Often I drink less than that. She has been suggesting that I start drinking the recommended 8 glasses of water a day. So for about two days now I have made an effort to drink that exact dose. My body is not happy. I guess my body is normally dehydrated, so now that I am hydrating myself my body is perplexed. I know eventually my body will benefit. But, right now I get headaches and I feel nauseated all the time. It takes tons of effort to finish each glass.