The thing is that it can vary with pregnancy and/or nursing. What you need depends on what is going on with your pregnancy, and so your doctor is the one who would know that. I agree with grannynancy and suggest that you work with your doctor and the other resources wherever you are getting care. Your facility may have a nutrition expert who can talk to you about how you can healthily work with your weight and still keep you and your baby healthy.
When I was pregnant and nursing my kids, I also did NOT work to lose weight at that time because all those toxins are stored in your fat and are released when you burn the fat, and I did not want to have them in my blood stream and going into the milk.