I would talk to a lawyer if I were you.

The longer you are together, the better his chances of getting alimony from you due to his health and limited earning potential as a result.

The fact that he kept a serious health issue from you will be to your benefit if the marriage is short term.

I'm not saying rush out and get a divorce, just educate yourself on what your liabilities could be. Often, the first consultation with a lawyer is free.