My mom new I was pregnant before I even took the test. I lost alot of weight in my face and belly. It was noticable easpically since I am chubby girl to begin with. it was almost three weeks before the other symptoms kicked in. There are alot of websites (including this one) that will give you some excersie tips for each week of you pregency thats good for you and your baby :) good luck and congrats
If you were my patient, I would advise you that purposefully losing weight while you are pregnant is not recommended. That is not to say however, that you must gain. In fact, for overweight to obese patients, gaining as little as 10lb for the entire pregnancy is an excellent goal. Similarly, we don't recommend suddenly beginning a new intense exercise program. Continuing the exercise that you have been doing, or even gradually increasing your fitness level is fine--swimming is an excellent way to exercise during pregnancy.
Hope this helps!