I am 8 years 5 months sober. AA was not for me.
Talk to your DP. Be absolutely honest. Tell him you know he knows, and that you want to stop. Let him support you instead of shutting him out. Shutting him out is damaging the relationship as much as the alcohol.
Go to your GP as soon as you can, ring for an emergency appointment. This cannot wait. Be honest with your GP.
There are medications for diagnosed Anxiety. Drinking regularly can make generalised anxiety much, much worse. Your brain, nervous system and adrenalin levels are totally scrambled by alcohol, driving your body into a cycle of 'flight or fight'.
I was a functional alcoholic, I had a very responsible job, ran a second business. There is no one 'type' of alcoholic.
I don't believe in controlled drinking. I can never, ever have a drink. Because one is never enough. 10, 15, 20 are never enough. You are 'doing deals' with yourself, breaking them and then thinking 'fuck it. I may as well have the rest now because I've blown it. I'll try again tomorrow' thus ending up in a cycle of guilt and self loathing which actually means you're drinking more than ever. This a common across all addictions from alcohol to gambling.
I haven't relapsed. Yet. I hope I never do, but it's always a possibility. I needed to get sober to get to the bottom of my drinking through counselling. Once you get to the 'why', a lot of things click into place.
There are lots of good resources already mentioned in this thread and the addiction support boards on Mumsnet are really supportive.
You can do this.