To expect some kindness and empathy from DH

[Tonytonitonee]

I have been feeling unwell for a while now and am on medication for thyroid issues & a couple of other things. I usually feel horrible, depressed and exhausted.
DH no longer cares. If I tell him how I am feeling he'll listen for a few minutes and then try to change the subject or tell me to go and see a doctor. We have been married for 12 years and have two children. I have been feeling unwell for a few years and have been going to the doctors but nothing seems to work, and I feel like crap.

Today, I was telling him how I was feeling and he was looked bored. I challenged his behaviour & he became defensive, telling he isn't a doctor so he can't help me. He went on to complain that he had his own problems. I understand he is stressed at work but surely he can just listen, even fake interest for 5 minutes.
He is a present and attentive father but he is seriously lacking as a husband.

Bless you. That's a really intense medication. I was too scared to take it when I was offered it.

No wonder you feel poorly.

I have got a friend who complains too much, but you sound nothing like her! She can tell you fifteen or twenty times in a row that she's tired. You can't get a word in. In comparison, you're absolutely fine!

Very few people can continue to have empathy after several years of several times a week. I’m glad you can. You can step up for your empathy queen award, but the fact others might get to the end of their tether doesn’t mean they lack empathy,

Your evidence of this is...?
There is ample evidence of just the opposite.
For example, millions of people all over the world care for ill, elderly relatives and manage not to lose empathy. They not only have to listen to complaints, they have to change diapers, spoon feed, try to provide distraction from suffering by reading to the person, plus many other tasks. This is by no means exceptional, it's actually extremely common. These people don't consider themselves "empathy queens" anymore than I do. They see it as quite ordinary and a natural byproduct of love and commitment.
Empathy isn't the ephemeral thing you suggest it is. It does not "wear out." It's there, in whatever quantity the person has of it (be it high, low or average) or it isn't.
People do get tired out from long term caregiving, but they still care. It just means they need a break and should take one. But OP's husband is not a caregiver. This is not a case of compassion fatigue.

You're partially right though. Being irritated by hearing about how somebody is feeling for five minutes a few times a week may just say the person has a tendency to be impatient and intolerant. Or it may say they don't love that person deeply enough to keep on caring over a long term. It's possible that with a different person, they might feel differently.
What other possibilities are there, in your view?
"I love you madly, darling, but I regret to say that my empathy tank has run dry from hearing about how you're feeling." is not going to fly. It just doesn't work that way.