When were you diagnosed as having ADHD? If it was diagnosed before 12yrs then you can be suffering from adult ADHD acc to DSM- 5. Due to improper connection between frontal lobe and rest of the brain, you are susceptible to addiction. Brain is trying to heal itself by getting whatever substance makes it feel relaxed.
Next Steps
Try EEG based neurofeedback and meet a psychiatrist to start medicines for you.
Health Tips
Be in proper treatment plan and don't self medicate.