Trouble with weight gain : 24 weeks

So at my last appointment I weighed 137lbs. I was 21 weeks. I weighed myself tonight and I’m 136lbs at 24 weeks. I’m having the hardest time gaining weight like I should. My OB gives me the Ensure protein shakes every time I go to the doctor (even though I have a whole fridge stocked full🤦🏻‍♀️😂). I just have no appetite lately. Besides the protein shakes, is there anything else I can do to keep up the weight gain? I was really underweight when I got pregnant.