I wish you had given me a little more information. With so little, I can only give you the most general comment.
Yes, withdrawal causes lots of unpleasant and sometimes surprising symptoms. Much depends on what you are addicted to, how long you have been addicted, and what supports you have as you withdraw.
Addictions, in general, change your brain chemistry. Often addiction interferes with concentration, memory, and motivation. It can therefore look like ADHD. When in doubt, check it out, of course. But I’m guessing that the addiction is the issue, not attention deficit.
Addiction can also decrease someone’s tolerance for unpleasantness and pain to the point that they avoid situations where they might be uncomfortable. Over time, it’s possible for someone who is addicted to be convinced they don’t have what it takes to manage the stress and discomfort of getting through recovery and managing the ordinary difficulties of life.
I wonder if what you are experiencing is that avoidance of discomfort. Having been used to a way out of stress through addiction, you may no longer trust your skills for managing feeling bored or stuck or unable to understand something. Rather than persevere, you drop out. Not finishing does make you feel better because you can always tell yourself “If I did keep trying or if I did finish, the results would be great!. Of course, you’ll never really know. But sometimes people think that not knowing if you’ll fail is better than trying and finding out,
I hope you are getting support for withdrawal. Again, depending on what you are addicted to (and for how long), the effort to get clean and sober can be more difficult than you imagine. You probably need, and definitely deserve, the counsel and support of a trained substance abuse counselor and maybe a program led by others who share in your struggle.
I urge you to find out what recovery groups hold meetings in your area. Don’t be discouraged if you aren’t comfortable the first time you go. Sometimes, the make-up of a group simply isn’t a match due to the program method or even such things as the time of day the meetings occur. If that’s the issue, try out a few different groups until you find one where you “click”. Sometimes the discomfort is due to not wanting to face that you really should be there. If that’s the case, hang in there. Talk to members about how to tolerate and stay attentive while you get accustomed to the philosophy, routines, and membership of the group.
Withdrawal is only the first phase of recovery. There’s more to it than that. You also need to learn why you are vulnerable to addiction and how to avoid relapse. Recovery takes courage, and patience, and commitment.
I wish you well,