Should I be paying taxes and insurance on uncle's house?

Jessiemae, do yourself a big favor and go see an elder law attorney. Document every payment you made in insurance and taxes. Estimate how much you spent on food, etc. Make a one page summary of all this info (don't pay for the time it would take the lawyer to dig through your paperwork!). This will cost you $200 - $300 but will pay for itself many times over. He or she will ask the right questions and advise you on how to best proceed. If your uncle-in-law is cognitively together, you may want to take him if you have a follow up meeting.. I wouldn't bring him to the first meeting because, in the interest of efficiency, you and the attorney will want to speak very frankly without mincing words.

You should NOT be paying his home expenses while he had the money. You won't get it back unless he sells the home and voluntarily gives you the moneybefore he had any need of Medicaid. You won't get the house because it's not in your name. And if he develops memory problems or dementia before he does sell, he will probably forget all about your having paid anyway.

Explain that if he doesn't want to pay the taxes and insurance, he needs to sell the home now and rent somewhere. Unless you have tons of money to spare, you need to be saving it for your own old age.

If I am reading the original question correctly, the house deed was transferred to you 5 years ago. Is yours the only name on the deed? Did it get filed with the county courthouse? If so, the property tax bill should be coming in your name. It is YOUR house, not his, and you are responsible for the taxes, insurance and upkeep. You could even charge him rent if you wanted.
What were the terms of you aquiring the house? Was it a gift or did you have to pay him something? Make sure that is all clear so once he passes, the rest of the family doesn't accuse you of undue influence and sue you for the value of the house. If you are buying his groceries, medication, etc, I would keep track of the receipts so if there is a problem in the future, you can show you weren't taking advantage of him.
If his name is still on the property, his interest in it would only be attached if he gets Medicaid (not Medicare) or if he has any unpaid debts and a lien has been put on the house.

I assume your uncle didn't put the house in your name because that would have interfered with the look-back for your aunt's Medicaid.

my current experience is as follows. My mother inlaw went into a nursing home on medicaid. I could not sell her home at that time because the market was bad. I paid the taxes and insurance (while it was insurable, some agencies don't insure vacant houses) I was advised to treat my payments for her home as a "loan" to her. One day when the home was sold I would present a bill ( like any other creditor) with proof of payments and will be paid back. If he ends up selling his home and eventually going to a nursing home you can also submit a bill then. I wish I had paid for everything from one account and kept EVERY receipt. Hindsite is 20/20 it would be a much faster job of proving the payments.

If it was put in your name OVER five years ago, prior to 2009, then it is already yours, and no the government won't take it. If it is still in his name, the government will take it if he applies for MEDICAID.