Plateau after just a week?

First ...

You might also check out these:
http://community.myfitnesspal.com/en/discussion/10300319/most-helpful-posts-general-diet-and-weight-loss-help-must-reads#latest

Especially the one entitled:

It is unlikely that you will lose weight consistently (i.e., weight loss is not linear)


Second ...

Sorry, but I doubt you're burning 3000 calories a day.

Enter your details into MFP.
Select Lightly Active as your activity level
Select an amount to lose (i.e. 0.5 kg/week)
Eat the number of calories MFP gives you.
Stick with it.

Are you working out? Could be your muscles retaining water.

I’m 100% sure I’m burning more calories than I’m taking in, but after a few days of suddenly extreme diet and exercise, the scale didn’t budge...but my clothing already feels lighter...I read it’s likely water weight.

I’d guess it’s the same for you, unless you are miscalculating calories or the amount of exercise you are getting.

Good luck

A plateau is generally considered to be something like 4-6+ weeks with no changes in weight while making no changes to your routine (since exercise and diet changes often come with greater water weight fluctuations in the beginning). So it doesn't sound like you're quite on a plateau yet, thank goodness!

I agree with those who are saying that you're likely just seeing some weight fluctuations and it's nothing to worry about. But if the problem persists, these would be my generic tips:

1. If it's been less than 3 weeks or so, don't sweat it! Normal fluctuations happen and unfortunately sometimes we stall for a week or two even when we're doing everything right. Give your body some time to catch up with the changes you're making.

2. If you aren't already, be sure that you're logging everything. Sometimes people forget about things like veggies, drinks, cooking oils, and condiments. For some people these can add up to enough to halt your weight loss progress.

3. Consider buying a food scale if you don't already have one. They're about $10-$20 dollars in the US and easily found at places like Amazon, Target, and Walmart. Measuring cups and spoons are great, but they do come with some degree of inaccuracy. A food scale will be more accurate, and for some people it makes a big difference.

4. Logging accurately also means choosing accurate entries in the database. There are a lot of user-entered entries that are off. Double-check that you're using good entries and/or using the recipe builder instead of someone else's homemade entries.

5. Recalculate your goals if you haven't lately. As you lose weight your body requires fewer calories to run. Be sure you update your goals every ten pounds or so.

6. If you're eating back your exercise calories and you're relying on gym machine readouts or MFP's estimates, it might be best to eat back just 50-75% of those. Certain activities tend to be overestimated. If you're using an HRM or activity tracker, it might be a good idea to look into their accuracy and be sure that yours is calibrated properly.

7. If you're taking any cheat days that go over your calorie limits, it might be best to cut them out for a few weeks and see what happens. Some people go way over their calorie needs without realizing it when they don't track.

8. If you weigh yourself frequently, consider using a program like trendweight to even out the fluctuations. You could be losing weight but just don't see it because of the daily ups and downs.

9. Some people just burn fewer calories than the calculators predict. If you continue to have problems after 4-6 weeks, then it might be worth a trip to the doctor or a registered dietitian who can give you more specific advice.