No weight loss after 3 weeks

It's hard to say without any details and a closed diary. These would be my general suggestions:

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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. You might also be sure your scale is working and doesn't need new batteries or anything.

8. 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.