I've been back and forth from the vets for months

[sarahhhh]

Hi girls, guys and non-binary friends. This isn't a nice post but I'm at a loss for what to do.
My old boy has had some health troubles, his eyes bulging, and a protruding scent gland on his tummy.
I've been back and forth to the vets for months now. At first we thought it was an eye issue so he had antibiotic eye drops, then we thought it was his chest so he had oral antibiotics and now the vet said his eyes are likely bulging due to discomfort from his scent glands so we've put him on painkillers.
He doesn't seem to be getting any better and I haven't missed a SINGLE DOSE. He's too old for surgery and I really don't want him to suffer like this anymore. He's eating and drinking but obviously because they're prey animals it's harder to know if he's in pain. He's also super itchy, I've checked him for mites and I can't see anything.
I need some advice, or personal experiences, or even some comfort because I'm losing my head. I don't know what is right for him. I know I can't ask for medical advice but I need to hear something from people who care about hamsters as much as I do xx