Hi WaterofLife and welcome to SR.
I was a heavy drinker but I found that I had to control my drinking. I was actually very successful at it and spent a lot of time sober, rather than drinking. In fact in the last stages of my controlled drinking I drank much less than I did in my teens and early twenties.
Then one week I went away on holiday. I don't even think I had drunk at all in the weeks leading up to the holiday and, of course, I was looking forward to relaxing and enjoying some drinks. I came back from the holiday an alcoholic. I no longer had any control over alcohol. It took me another two and half years of desperate uncontrolled drinking to realise that I was an alcoholic.
Somewhere during that week away I crossed an invisible line from problem drinker to alcoholic and I could no longer go back. It wasn't the quantity of alcohol that I drank that week that made me cross the line, it was the fact that alcoholism is a progressive disease - it always gets worse, even if you are not drinking.
I hope you are successful with your moderation. Some heavy drinkers do find that they are not alcoholic and can quit or cut down when needed.