I'm glad you posted and I hope you decide to stop drinking. Alcoholism is a progressive disease and it will get worse unless you stop drinking. Blackouts are horrible and dangerous, especially for a woman.
As far as your wedding and your best friend's wedding - it's about making a choice. There will ALWAYS be a reason to drink and a reason to not stop drinking, always. It's just a question of doing the right thing for yourself and your life.