Well he may be a bit of an ugly duckling, but he looks like a sweety! No CC as it ihas already been done. Keep in contact with your vet and maybe try adding fat and more calories and a balancer to his diet to help build his weight. Have his teeth been floated recently? He may not be eating enough hay due to tooth pain.
As long as he is sound and happy and you are happy with him, work on his weight and just enjoy him.