Weight loss?

It's only been 3 days since I found out I was pregnant, and I've lost 5 pounds! I haven't got morning sickness and haven't cut down my food intake either! (I usually eat more than I probably should.) I've never drank pop or caffeine in my life so I didn't cut out a lot of sugar either! I still feel fine and tests are still dark but every morning it seems another pound melts away!! I'm thinking my metabolism might have reared back up to its high school level or something!