There could be a lot of reasons, so let's explore some of them.
1) You may have lost a large amount quickly and your body needs to adjust.
2) Most commonly, we get sloppy. Start measuring your portions and recording them immediately. If we wait, our memory gets 'loose' and is not as accurate. If you have a smartphone, download the app so that you can record anywhere. If you don't keep a small tablet or paper close to immediately write down your food. When I eat out, which is FREQUENT, I always record before it touches my lips.
3) Have you increased your exercise greatly? Muscle is more dense than fat, so you might be losing inches while your weight remains the same.
Use other measurements of success for a couple of weeks. Measure inches (I don't. It is something that I don't feel is accurate for me). Called NSVs (Non Scale Victories) you can use clothes to determine weight loss. How do they feel? Are they looser, more comfortable? Can you fit into a smaller size? Are people commenting on your weight loss? How do you feel personally? Are you feeling more energetic? Healthier?
I just stayed the same (plateaus are also known as 'practice maintenance) for 1 month, then lost 8# in one week! The fact of the game is, if you are loyal and persistent, the weight WILL come off. It has too! Keep pushing and success will be yours!
You can do this. Just