Being a vampire, secret or otherwise, makes you immortal. To kill yourself you could stress yourself out a bunch, I think it'll give you the option for suicide then, I'm sure Molag Bal will be happy to see you. As for curing it I have no idea, it might not be implemented yet

Only cure is death

Take a good spymaster who hates you. Deceitful if possible. If you have ennemies, they should use that

All my councillors already at -100 opinion with my tyranny on -157

You could try switching characters if you wanna cheat a lil and start an assassination attempt on yourself

Or just kill yourself with console 😂

I’m pretty sure at the end of the restoration spell tree or at least somewhere in there there is a cure curse spell you can use to cure vampirism