Realistically, dramatic weight losses like that aren't usually the result of fat loss. While you are no doubt losing some fat, it's very difficult to create the kind of calorie deficits that result in that kind of fat loss. SO what you probably saw was the loss of retained fluid. It's really common to shed water weight like that! Especially since you "gained" that extra weight after only a few weeks... I'm betting you binged a bit, and were just bloated.
A one-off big weight loss isn't going to hurt you, especially not just four pounds. That's hardly outside the range of normal for starting over. I'd say that if it were to continue, that would be concerning, but right now? Celebrate and keep moving forward. :)
Writer, mother, wife, and breadwinner. I love to run, but running doesn't love me, so I'm switching to my low-impact bike.
I'm not pregnant, just fat: My blog. fatnotpregnant.blogspot.com/
| current weight: 187.4