Thank you all! I'm so glad I decided to finally post on here. I'm going to book that appointment tomorrow during my lunch break, your replies gave the courage to finally go through with this.
My manager is one of my closest friends and also 2 years sober. She's kept me employed and supported me throughout this, without her I probably still wouldn't have admitted that I have a problem. She's had to put up with so much from me. I owe her big time, I'm extremely lucky to have met her.
I know I'll regret it in the future if I don't get myself back on track now.