I have had a lot of fliuds today and took a pregnancy test this evening and got a negative result could the fliuds have affected the test?

Yes, this is possibl: If you drink enough water you can dilute your urine down to the point that the amount of substance being measured is below the threshold for a postiive test. However, this would only happen if the amount of HCG in your urine was fairly low to begin with.

Possible: In early pregnancy HCG is low enough to get a false negative pregnancy result if you drink enough water. Why are you trying to create a negative test result? Correct way of doing pregnancy test is by using first morning specimen to ensure that urine is concentrated. See this site of HCG levels by week. http://www.americanpregnancy.org/duringpregnancy/hcglevels.html.