You really shouldn't try to lose weight while your pregnant. Worry about that after you have the baby. Just try to eat well right now. You need dairy for calcium. Trust me, I wish I could lose weight right now, if it weren't for baby I wouldn't even eat. Just eat healthy and you will feel better.
Lots of steamed/raw veggies and fruit stay away from chips/breads/ cheese and reduce your dairy intake. No greasy fried foods and only consume natural sugars(fruit) in 3 weeks you will see not only a difference in weight control but in your health and energy too!