Too much weight?

13 lbs at 25 weeks pregnant. Have I gained too much? I was 25 pounds overweight to begin with... My Dr. said at my 20 week appointment that I don't need to gain anything during my pregnancy since I'm so heavy, but not gaining is so hard! I eat rationally and exercise EVERY DAY at least 30 minutes but still my weight seems to be going up. I go to bed hungry every night and it makes it hard to fall asleep. My belly gets bigger all the time but my butt fits into my pre-pregnancy jeans so all of my weight gain can't be fat right?