How do I challenge a prenup agreement if it’s unfair?

When my husband and I met we both had good careers. I never expected to leave my job so I signed a prenup waiving my right to any alimony. After we got married, we had a son who is disabled. He needs full-time care, so I quit my job to stay home with him. My husband encouraged me to do this, since neither of us wanted our son to be cared for by a stranger. Things with my husband have gotten rough over the last year and I am worried about how I will support myself if we divorce. I know he’d have to pay child support for our son, but since I signed the prenup, I’m not entitled to any alimony. Is there a way for me to challenge the prenup and get it overturned, or at least modified, because it’s no longer fair to me?