Thirty weeks, weight started growing rapidly. I see my doctor every we…

Thirty weeks, weight started growing rapidly. I see my doctor every week. Now she said to come in one day later, because I gained 1.1 kg in a week. I don't eat anything harmful, I don't understand where the extra kilos come from. The gynecologist says if you don't lose it before December 31st, they will put me in a hospital... Suggest how to lose weight?