Are you eligible for disability benefits? They may be much easier to get then alimony. If you were diagnosed after you separated, he has a very good case.
I'm on the opposite side of such an argument right now. My partner let his ex-wife take everything when they separated, because she is on a disability pension and under Australian law she could, if she wished, claim maintenance payments from him for the rest of her life. He has been very accomodating towards her in the hope that she will not make such a claim.
No-one pays money for no reward if they don't have to. He must, of course, pay for your daughter, but if you want him to support you too expect to have to fight for it.