What happens if you can't get mortgage protection?

Let's say you can't get mortgage protection because of health issues, and can't get an exemption from the bank, is the social housing the only option?

I'm applying for mortgage protection. My diagnosis is bipolar 2 but there have always been question marks about the accuracy of that, I think on my file they actually have major depression down. I've never been hospitalised or missed work, but I changed my meds 6 months ago.

Also I've got dyspepsia and PCOS. Kind of concerned about what my premium will look like, if I even get one.