During childhood I struggled with ADD (now diagnosis of mild ADHD). I did take supplements (mainly vitamins to make sure I have everything I needed), removed items from my diet high in sugar and anything else the irritated me (cleaning supplies, certain candle/airfreshner scents). That only went so far, I still had a horrible time in school because I just could not focus, meds really helped me A LOT. I took them through high school but stopped in college. Meds was a last resort after trying all of the above, if the improvement only goes so far then it really is ADD/ADHD but if all the symptoms go away then it is a misdiagnosis.
I have not taken meds since freshmen year of college for now I have my ADHD under control enough to function without it... BUT my doctor has told me that with age it will get worse and might need meds (they really do make a difference when I took them, even after the diet/supplement changes).
Also the stress is killer for someone with ADHD, not completing something, lost of trust with family add even more stress which will trigger even more of the ADHD symptoms and it really snowballs from that and is really hard to get out of without A LOT of help and maybe even meds!
Some books that have helped me:
Stress Can Really Get on Your Nerves! by Trevor Romain & Elizabeth Verdick (this is geared towards young adults but find it very helpful even if not in school any more)
Survivor Personality by Al Siebert
Being the Best by Denis Waitley
Time Management for Unmanageable People by Ann McGee Cooper
You Don't Outgrow It by Marnell L. Hayes, Ed.D
Succeeding Against the Odds: Strategies and Insights from the Learning Disabled by Sally L. Smith
There are many more books out there that are helpful these are just a few that I have the names of.
Support groups (for you) are also helpful but I have not gone to one, due to having my ADHD under control and not search one out.