Try low carbohydrates, high protein meals. There are many hidden carbohydrates in our daily food (Eg Gyoza, Spring roll, fried food). Cut down on sugar drinks and sugary snacks too. I also face same problem. From week 25 till now week 30. My weight never increase but baby growing healthy. I’m at 10kg weight gain - 30 weeks pregnant. Maintained same weight for 5 weeks after the new diet recommended by dietician.