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If your husband works and earns money and you are broke and have no insurance then he has, by default, proven that he is not doing a very good job caring for your financial condition. It is possible he knows this and that he say's no to you because that feels easier than hearing you say you need something he can't provide. He may argue the details and semantics or throw camouflage up to disguise the issue because it deflects the focus from what a bad job he has done taking care of you. You can take the high road and not use that language, not intentionally point out his failure. Simply stay on focus. The focus of the conversation needs to be that you are an adult and can make your own decisions. That healthy married couples make decisions about these things together.

In California, all money earned in a marriage belongs to each of the two spouses equally. The law doesn't define who gets to sign checks. Incidentally, all debt, including the debt of his business, belongs to you as well. If you are a stay at home mother to 2 small children and have not worked at your husband's insistence, I suggest that you have a conversation structured like this:
'I need_______and that will cost $_____. Let's set up a plan for when I will be able to have it.
I need and want to work to help provide for our family and for myself.
I am fearful that something will happen to you and I wont be able to care for myself and our children.
I need to know what our financial situation is, what we earn and what we spend it on.
I need to be involved in the process of managing our money.'
This should include the books for his business.

If it were me and he said no, I would let him know that it was no longer acceptable to me to live this way. This is not a threat. It is a statement of fact. It can sound like this. 'I need to be involved in the process of managing our money. It is not acceptable to me that I don't have any control over my financial security. I want to go see a professional to discuss what we need to do to get our financial house in order. We need to work as a team to develop a plan for our financial future.'

I would not take no for answer. Your future depends on this. There are free services provided by the government to help consumers manage debt. One such organization is www.ConsumerCredit.com and they will provide you with advice with or without your husband's agreement. Good luck with it and let me know how it goes.