OP I really feel for you - you're between a rock and a hard place. Loyalty to OH, yet aware something is radically wrong and it's on your conscience.
I agree with those who say you (albeit unintentionally) are minimising his addiction. It doesn't affect patients. He's in control. Etc.
Please, if you take nothing else away from this thread, please please believe that your OH will not have told you the extent of his addiction and the lengths he has gone/will go to, to get his 'fix'. Whether that be going round numerous pharmacies to get his codeine so suspicion isn't aroused (I apologise if codeine isn't the drug, but it's the most common and you haven't denied it when hinted at in this thread). Or 'doctoring' scrips at work.
Ultimately, while an addict he's a danger to himself, and a danger to those he works with/for whilst actively addicted.
I know how hard this is. I know how you absolutely believe he would never harm anyone and isn't a risk. I buried my head in the sand too.
I had to give an ultimatum at the end of day - either he got help, or I would report him. It tore me apart but I knew in my heart of hearts I would never forgive myself if anything had happened to my child, his clients, or even to him.
Please take the blinkers off x