If you are starving, you should eat, that is your body's way of telling you you are cutting calories too much. I kept my bottomless pregnancy appetite until about 4 months, when it shut off like a switch. (Interestingly, that is the same time I got my period back)
Be sure you're getting plenty of exercise, as your dr. says you are allowed. Doing cardio intervals (such as walking on hilly terrain) and light weight training is the best way to burn fat and increase your metabolism. Do work up to it slowly and be careful of your joints, as you may still have loose joints for some months after birth - I still had loose joints until my dd was about 5 months, which made jogging out of the question, for example - I jangled all over like a marionnette!