Hello, Sweetzer, and welcome to the forum. You will find there is lots of support and a wealth of experience here among the members, and you never feel quite so alone with things!
My husband initially was diagnosed by his gp, who sent him for an initial appointment with a psychiatry of old age consultant, and a CT scan. My husband had the scan, which was clear and showed no sign (apparently) of alzheimer's disease. The consultant managed to do an initial test, which my husband could have done with his eyes closed and one hand behind his back! But the consultant knew he had dementia, his gp knew he had dementia, and I knew it. My husband, however, furiously denied that there was anything wrong. He refused to go back to the consultant again, because the word "psychiatrist" was on his door, and refused to undertake any more tests, and refused to take any medication.
It was nearly three years before anything changed. By that stage, his paranoia and delusions had grown by leaps and bounds, and he was hallucinating 24/7. He was living in his own personal horror film, so he was happy to go to the doctor for help, happy to go back to the consultant (who he came to think of as his best friend!), and happy to take whatever medication they gave him.
Sometimes, you can get a person to go for help. Sometimes, you can't. Or not until, as you say, things have progressed. You could try (if the doctor was agreeable) making an appointment for yourself, and asking your husband to accompany you. I used to do that, and the doctor would take a quick look at my throat, listen to my chest, all the while chatting away to my husband, and then he'd say "Seeing as you're here, I'll take a quick look at you too! Two for the price of one, eh?" Of course, your husband would probably realise if he was being tested! In the meantime, I suggest that maybe you work on practical things, like getting power of attorney in place . You could do one for yourself too. And making sure your Wills are in order. Separate as much as you can, your finances from your husband's in case he needs to be assessed for Care in the future, as only his savings would be taken into account.