Does diet pills, not eating, four-six bottles of water affect the pregnancy test results?

In very early pregnancy, excessive fluid intake could possibly effect your results. This is why it is recommended to take a pregnancy test first thing in the morning. Diet pills and not eating would not have an effect.

It is not uncommon to be late now and then, and it could possibly be due to the diet pills and not eating. Periods can sometimes be effected by substantial changes in weight... in particular weight loss.

Wait another week and see if your period is just off this cycle. If still no period, try another test first thing in the morning, following the directions exactly.

Since it appears you are trying to lose weight... consider going about it in a healthier way. Cut back on how much you eat, make healthy food choices, and get some regular exercise. Sure it will be a slower and steadier weight loss, but you will be healthier and your body will be able to function as it is designed to. You also will have a far greater chance of keeping the weight off. Excessive dieting is exactly why you see so many diets on the market and why people frequently go up and down... it simply is not something that can be maintained and the potential harm you do to your body can be disastrous.