In retrospect I think I must have known all along, but just chose to ignore it
The first time I drank I stole some beer and hid it (aged 12).
I used to steal bits of alcohol from my parents drinks cabinet and hide it under my bed.
Every time I went out I always ended up so much drunker than all my friends until an embarrassing incident aged 17 and I started being really careful.
After college I noticed that most people didn't drink like me so I started to hide it.
Having 2 bottles of gin, one which I kept under the sink to top the other one up so that people who came round regularly didn't notice how quickly I got through it.
Preferring to drink alone so that I could drink properly.
I actually stopped recycling because I couldn't bare to face the empties.
Limiting the amount of booze I would buy because I knew that if I had it in I would drink it all.
After months of really bizarre migraines I finally got some medication on prescription. When I picked it up from the pharmacist I asked if I could drink on these...The pharmacist looked really confused and said she couldn't understand why I'd want to.
After being told by a medical professional that I should stop drinking entirely, I continued to drink for months (maybe it was a year...)
I'm sure I could think of more signs...