HUNGRY!!!

I am 19 weeks preggo and hungry all of the time!!! I was told by my midwife that I was gaining weight too quickly and to begin in watching my calories. So I have been staying within 1600 calories. However, I work out 5 days a week and burn between 500 to 1000 calories just in my workout. So I am wondering if I am not eating enough. I don't want to gain unnecessary weight but holy guacamole I want FOOD!!