Is my disability subject to alimony

Sounds like this belongs on the family law board. The answer to your question is maybe. It's impossible to answer without knowing more but suffice it to say that it could be under certain circumstances.

If you mean do you have to pay if you're on disability.. Yes but only if it was a non-modifiable court order..
If you mean do you have to claim it. If you're talking about SSD then no it does not count as income if it's court ordered, only income from wages earned have to be claimed. Even if you win the lottery its not considered earned income.
Now if your talking about Federal Disability that's a whole new ball game. You have to be careful with them.
Hopes this helps.