I really think you need to log your food to see what's going on. I personally have been active and fit most of my life and still I gained weight and it was all due to diet. For the average person, diet is about 75 percent of weight loss, exercise 25 percent. So if you never exercised before and you start you may lose a small amount of weight.
If you log your food for a week, it'll probably become much more clear what's going on.
Fitday start date 12/9/12
Fitday start weight 190
Highest weight Jan 2009 218
Lowest weight Aug 2009 175
Goal 160: ACHIEVED Aug 25/13 (now to figure out how to stay here)
If you do what you’ve always done, you’ll get what you’ve always gotten. –Tony Robbins