Congratulations on losing the weight. Don't feel discouraged at all, you have already made a step onto a great self.
Now as for the plateau it can be due to many reasons. What is your training regimen? How many times a week, and do you do cardio, weights or both? To track calories as accurately as possible you preferably should get the APP myfitnesspal from itunes app store or google play and a food scale if you cook at home. You see carbs and protein each have 4 calories in them per gram and fat has 9 grams. Also if you've been cutting back 300 calories from your daily intake then you should consider lowering it slowly, day by day. Going to 500 up to 1000 calories. You don't want to feel lethargic though. I usually stay between 500-1000 and won't cut my intake more than 1000. It can be too drastic. Also if you have been doing the same routine over and over, your body will be use to it. You need to give your body a reason to lose fat. Switch your workout up, maybe try HIIT training. Also note that the body loves to keep fat stored for ''survival'' reasons. It is in every humans genetic code. This is why pro bodybuilders cannot go to 2% body fat without using drugs because it isn't natural. My point on here is to slowly cut back calories, I recommend to eat your calories normally again for a few days then start cutting them back again, as the plateau could even be due to you cutting back too many calories too fast and now he/she does not want to lose weight as it is naturally scared you may be losing fat too fast.
