Your rabbi is trying to point you in the right direction, but he might not be aware of the details and struggles that you have. As others mentioned above ADHD people have a hard time keeping to a routine. If you can schedule yourself (and follow it!), great. Otherwise, wallowing in self-pity and despair will probably send you spiraling out of control.
It’s best to do whatever is necessary to help yourself. Some have success with “mindfulness” – paying attention to breathing, davening, etc. to stay in the moment. It trains the brain to focus and can help in the long-run. But if it’s wreaking havoc on your life, it might be wise to discuss medication with a professional – even if only used temporarily while working on yourself.
All the best