Re: Is this what I've lived with for so long?
Your symptoms certainly sound ADHD-like. The problem is that ADHD has become something of a 'catch all' diagnosis of late with many doctors taking the shortcut of calling any inattentiveness or impulsiveness ADHD without exploring alternative diagnoses.
If you feel like you may have ADHD and you can afford it, get yourself a full physical, checking for any conditions that may lead to ADHD-like symptoms. After that, consult a mental health professional and have a proper diagnosis done. Just hold anyone diagnosing you accountable and make sure that the diagnosis makes sense to you. When seeking my own diagnosis, I ran in to a number of lazy professionals with pet causes who did me more harm than good (sounds like a catch-22, I know). Get a diagnosis, but educate yourself and don't accept something that doesn't make sense.
If you're in a situation where you can't afford a proper diagnosis, in many cases you can walk into the office of a general practitioner these days and walk out with meds (I've heard of people being diagnosed and medded because they were late for their appointment). If you can get a diagnosis from a GP, give the meds a try and see how it goes. The beauty of ADHD meds is their effect is so general they can help with your focus problems whatever the source, at least temporarily. This may help you get through school or whatever until you're into a financial situation that allows for a better exploration of your issues.
Note that I am not suggesting deception or illegal behaviour. No matter what you do, make sure it's on the up and up.
Best of luck