Too much, Too fast

I had my 20 week appointment today and my doctor said I am gaining too much weight, too fast. I have gained a total of 8 pounds in 20 weeks. My doctor would like me to stay between 20-25 pounds throughout my whole pregnancy. In order to do this, he has put me on a 150 calorie per day "diet". I am a little disappointed that I have to count calories, even when I am pregnant.
I have been on a diet since sophmore year of college and I was really enjoying this time in my life when I could just enjoy myself. I know it sucks now, but I will be more thankful when our baby is here and I am not left with 40+ pounds to lose. Stephen is going to watch his calories too, but we have agreed that we will wait until after Thanksgiving.