28 weeks Doctor told me to stop gaining

Brett
I'm so confused. I went to my ob appt yesterday and after telling me i was measuring perfect and baby's heart sounded great she told me i need to stay right where i am weight wise. She said the concern is the baby will be too big to deliver. Of course i take this to mean I've gained too much weight. I'm 5'7" and I've gained 50 pounds. I just feel like it's never good enough. Baby too small, baby too big. How are you supposed to have a perfect sized baby?