Hi, and welcome!
Yes, the first 2 weeks you lose the most. You're burning up the glycogen stored in your liver, and when you lose glycogen, there's some water that goes along with it. (See the sticky about ketosis for details.) At your starting weight, 4 pounds a weeks sounds about right. Like Jay said, most of us would kill to lose that much every week.
You may want to take some measurements, too. There are weeks you won't lose much, but those are almost always the weeks you'll see shrinkage on the tape measure.
Keep up the good work! I've been on Medifast since April, and I'm still motivated to keep going.
I lost 17 the first week, but only 4 each of the last 2 weeks
