I'm 195 lbs, and I've lost about 10 pounds. I'm not actively trying to, but I'm just not wanting things like carbs and sweets this time around. Last pregnancy was an entirely different story.
So yes, you can lose weight, though you shouldn't diet intentionally. Moderate exercise, like swimming and walking is fine. Basically anything your body was already used to can be continued.
Most doctors won't have you actively trying to lose weight when pregnant. Just try to eat normally--- eat a healthy balanced diet without overdoing the portions. And yes, exercise. but if you have not been one to exercise before, maybe check with your doctor. Here is an article that may help:
http://www.medhelp.org/pregnancy-health/articles/Pregnancy-Fitness-Exercises-for-Beginners/2220 Good luck to you hon