How many credits for SSD?

Here's my problem. I've been a stay at home mother and wife for years. My health was rapidly declining. Physical and mental I came to live with my sister and try to figure out what is going on with me. A neurosurgeon just diagnosed me with marfans syndrome. I've seen a statement saying I am 7 credits short of retirement ss, but when I went to the SSI office, they sent me a notice saying and not how many, that I don't have enough credits to even qualify for disability. I have an operation coming up and somehow or another, I have to find a way ..even if it kills me, to make up enough credits for when my condition leaves me totally immobile or blind