Possible next steps in rabbit that is not eating

English is not my first language so sorry for any mistakes. I hope to find some suggestions for next steps I can take.

Context: A male rabbit of 5 years old, neutured and 1.3kg. Never had any major GI problems, except for a few minor incidents where he seemed to be in pain/not eating which resolved within a few hours with some medication. He also has some problems with his eyes. When he was just a few weeks old one of his eyes was damaged by a piece of hay, and it took weeks to kind of heal. It left a visible scar and I don’t think he can see much with it. He was treated for E. Cuniculi during that time as well just to be sure.

Now to the issue: Three weeks ago he suddenly seemed in a lot of pain in his stomach, pressing his belly, did not want any food, kept to himself. We went to an emergency vet and got metacam, emeprid and cisaral and I gave him critical care. This time it took more than a week for him to get back to his energetic and playful self. That stayed like that for a week and then he went back to pain and not eating. We went to our regular vet and she diagnosed him with gas in his belly, but also a few hooks on his teeth and a bit more saliva than normal, but no wounds or anything. So we started the medication again and he showed some improvement; no signs of pain anymore but very selective in what he wants to eat and his droppings stay small. After a week they suggested to get him in to trim his teeth, which they did yesterday. I don’t feel like that was the issue, he is still very selective in what he eats and keeps to himself. He doesn’t look very happy and I’m worried that he is suffering. They now suggest it might be something with his eye, but it’s been like this for 5 years, why would this cause a problem now?

My question is mostly; are there other problems that can cause this? He is not drinking or peeing more than normal, last time the vet said his bladder was empty. They did not suggest any bloodwork, is that something I can ask for? I don’t want him to feel horrible longer than needed, how long do I keep giving critical care to keep him alive if he is not getting better? Any advice is appreciated, thank you!