I personally don't think a sub should have to be spanked or given some other attention in order to stay obedient. That just reinforces his bad behavior. That's not to say there isn't a place for spanking. And if you fear retaliation, then I fear perhaps he's not a safe partner for you.

You might enjoy the book Uniquely Rika. It's a little short for the price but the information is valuable. Alison Armstrong's book The Queen's Code is also really helpful. It's not about BDSM but it's about how women can more easily get their needs met without having to nag.

I'm really sorry you've had to deal with so many miscarriages and health problems. Remember that he signed up for "in sickness and in health" so this isn't a matter of whether you're too much trouble or him deserving a healthier partner. This is part of what he signed on for. Please don't consider yourself less of a partner because you're having health challenges.