It makes me extremely angry when I hear or read a story like yours. I won't mince words but your parents failed you in a big way. You were diagnosed and yet it appears nothing was done, no different than if you went undiagnosed or your parents ignored any symptoms and assumed that you were lazy, unmotivated, ect, ect,ect. I grew up in a time when little was known about ADD and it didn't have a name attached to the symptoms. My school days were nothing short of a living hell, and I am still paying a heavy price today(53, diagnosed at 37). I can't blame my parents entirely because of the unknown, but their parenting skills or lack of made a tough time even worse. If meds were available to me in grade or high school I know I would have had a much more positive childhood. Meds have been a god send for me but unfortunately to late to find success in career & relationships. My self esteem was destroyed.
What you need to do is make an appointment with an experienced medical professional, someone with knowledge of ADHD/ADD, since you were diagnosed as a kid but not told and nothing done you now have more control and input and the Dr. may want a current evaluation based on your perspective. As far as meds, there is nothing to fear. Meds are not a cure all and only part of a treatment plan but an important part . It's meds that will a positive effect on the difficulties your having. It is fear, ignorance and bad information that influence ones decision about meds, weather its the parents of an ADD child or the ADD sufferer themselves. There are numerous medications, what works for one person may not work for another, you may have to play around with dosages to see what works. I would also suggest that you educate yourself about ADD, many books listed here is a good start, there are several closed groups on Facebook where you can get valuable information from experienced doctors and ADD sufferers themselves. I would steer clear from anyone that has negative opinions about both ADD or Meds, most either don't have it or have an agenda. Scientology is notorious for spreading false and negative information about medications in general as they have an agenda against the Pharmaceutical Industry and Psychiatry community in general. But the most important thing is to educate yourself, that is key, the more YOU know the better. I would also at some point, if possible, ask your parents why they made the decision they did, they knew and chose to do nothing and you paid the price. I don't buy the " we did what was best" excuse, because that is exactly what it is an excuse. Parents are supposed to lay the foundation for there kids success in life, yours had the chance with your ADD diagnoses and the result of there failure was your difficulties in school and personal actions. Meds changed me for the better but after 40 years of difficulties in many areas trying to make that all up at my age is pretty much impossible. If I had been diagnosed in my early 20's I would have had a chance. There is nothing to be ashamed of by having ADD, and nothing to fear about meds. You are having the same difficulties that eventually destroyed me, you have the chance, a 2nd chance to change yours. Your parents failed you, don't do the same to yourself.