You probably hit a plateau. Everyone does, from time to time. It's your metabolism catching up to your overindulgence.
You can do one of two things. First, you can keep going as you are, and you'll pass the plateau within a handful of weeks or maybe a month or two. Second, you can increase your calorie intake. Although that doesn't always work - sometimes on these plateaus, you just have to wait it out and let your body catch up.