Second pregnancy, changed gynecologist because of the long road to her…

Second pregnancy, changed gynecologist because of the long road to her. (She was a very good doctor.) Changed to another one closer by, scolded me for not gaining weight, I told her that I eat, but she can't see me at home in the situation when my mouth is empty. Although I am naturally very thin, I don't know how to explain it to her. During the first pregnancy, the belly appeared only at the 7th month (and everything was fine), and here I was scolded like a director in the office. What could be the problem with underweight?