Starting a new Diet & Exercise... Need good tips!

We have been having trouble Conceiving…. Doc says I should lose some weight and I should be Preggo pretty quick! So I’m on day 3 of my diet & excercise – im super excited about it, I’m running and starting an Aerobics class! But my husband thinks im not eating enough…. but I just want to stay low in fats and calories….Help with any meal ideas or exercise tips??