same here. my gynae advised to eat as much as possible. drink more milk and eat more red meat to help baby grow. usually i get full very fast so she advised to eat every 2 - 3 hours in small portions and drink whenever i can. try your best to eat whenever possible. My usual drink is coconut water, date milk (farm fresh kurma milk) and soy milk. my food is beef, oats and lots of fruits.
The fastest and surely help to increase your baby's weight is avocado or materna milk. I don't recommend durian cos of it's very high sugar and also not the season so very expensive.