You can try healthier fat such as avocado (can do avocado egg spread / avocado milkshake / just eat on its own), unsalted baked nuts & seeds, additional olive oil into your food
I drank materna milk to help my baby gained weight cos I don't like avocado. It helps! My baby came out at 3.1kg at 37 weeks. I only drank once a day before bedtime.
Try avocado