Congrats. Take the W! If you are big and have a lot to lose it is not surprising. Just don’t be discouraged when that slows down. Even losing “just” 2lbs a week is considered fast weight loss, to keep things in perspective. :)
We’d need more data to give you a solid opinion. What’s your age, weight and gender? And what are you eating normally?
You could be going a bit too low with your caloric intake, you could be alright. It’s impossible to know without further information.