Nailit, just for you... I was an alcoholic from about 13-20. Only managed to stop as I was pregnant... and felt too guilty. I smoked from about 21, that was very all or nothing. I think I have the kind of personality where I can't go by halves. Both my parents were alcoholics (my mum, more briefly. My dad, always). To some degree, I think it is inherited, and I no longer smoke, as if I did, it would be full-on.
I "dabbled" a little, but nothing much. Nicotine is the hardest to stop and alcohol- cut down first, if you can (just my experience).
The majority of addictions, are hereditary- or self-medication. You need to honestly work out which, as both are treatable in different ways.
Antidepressants can be hugely helpful with alcohol or drug addictions.
Speed, is often used by people with ADHD.
People instinctively know what their minds and bodies need- but- you can get safer, nonaddictive, legal drugs to replace them. If alcohol is the biggest problem, it could actually be as simple as anti-anxiety medication.