Help, goat isn’t gaining weight

He’s almost a year old now. He’s a fainting goat. You can’t tell too much in this picture but his sides are sunken in. He has a little bit of a belly, but his hips are just sunken. I feed him a lot, make sure he forages. But he never seems to gain any weight. And now, he’s sleeping a lot, distancing himself from the others, walking slow, has eye discharge and a cough, and seems like the life has just been sucked out of him. He’s my best friend, and I can’t lose him. If anyone has any suggestions or ideas, please let me know. I’m desperate.