what does being "diagnosed" entail?

i really need some answers and judging by many of the posts, a lot of you are really educated and up on all this ADD stuff since by having ADD, you learn things as you go about doctors, meds, and ADD in general.

to begin with, i have heard that “getting diagnosed” is not clear cut because the disorder is so complicated, since it can be tied in with any of several other factors like depression, learning diabilities, personality disorder, autism, etc. That it’s not always easy to just go to a doctor and get them to say you “have ADD” or “dont have ADD”. Even doctors say it’s hard to know exactly 100% what’s in someone’s head and they are still in the process of mastering how to treat ADD (since they often have to do “trial and error” to see what meds and dosages work best for YOU specifically). I’ve heard that just going to a doctor where they have you fill out a checklist of whether you experience the common “symptoms/characteristics” of ADD is not enough, because I guess if that’s all they based a diagnosis on, it’s certainly possible that a patient could lie when answering the questions so that even if they answer yes to every “symptom” of ADD, they dont have ADD at all.

well, after i was convinced I had ADD after reading up on it and taking online “tests”, i went to my doctor. He is a general practitioner but also has years of experience dealing with ADD adult, and ADD kids. He follows the DSV-IV (or whatever that thing is called) guidelines of how to diagnose (the thing with the special criteria that addresses inattentiveness, hyperness, and impulsiveness).
After i explained to him my symptoms, characteristics, and daily difficulties, he had me fill out some simple questionairres (basically, one with checklist questions re: inattentiveness, hyperness, and impulsiveness; and another to rule out depression; another to rule out alcoholism/drug abuse). finally, he asked whether i remember having the same problems i’m having now as a child before 7 years old (which is another part of the guidelines). i’m 30 now and i obviously cant remember specific things from that long ago, but i was able to come up with a few examples of inattentiveness, impulsiveness, and absentmindedness. And with just that, i was “diagnosed” with ADD. Also, my weight, temp, and blood pressure were also checked, so i dont know if that counts for a “physical” or if a physical is even a crucial requirement.

I’ve heard that a complete and thorough examination is needed, even possibly taking IQ tests and having a phsyical exam, to get diagnosed for ADD and that merely filling out a questionairre is not enough. I would also think that since this is a neurological disorder, you would need to see a neurologists or at least get a CAT scan of my brain or something. But since my doctor has years of ADD experience, was obviously going by the DSV-IV criteria (even though it was basically through questionnaires), he ruled out depression/alcoholism, and asked about my childhood…does all this count as an official and reliable diagnosis?
I hope you dont say i have to get a second opinion, because unfortunately i dont have health insurance and i cant afford that right now. I really totally think I have it since I experience just about EVERYTHING I have read about ADD (except the hyper stuff)

thanks for listening!