As per my disclaimer, I have nowhere near enough knowledge to be able to tell you whether or not you display symptoms of ASPD- I am just giving you my own non-professional perspective on the situation.

Faking ADHD to get Adderall does not hurt anyone.

This is not true. Because people fake ADHD, docs and the general public are skeptical that people diagnosed with ADHD actually have ADHD. This means that people who truly have the disorder frequently have to suffer undue scrutiny from their docs when being prescribed meds, and may even have to suffer through not being able to get much needed meds if their doctor mistakenly believes that a person with true ADHD is faking it. This person will suffer from not getting the help he/she needs because doctors are primed to look for fakers because there are people out there who fake it. A student with ADHD may be treated with disrespect and may even be denied much needed accommodations because the teacher/school believes they are faking. Why would they believe students are faking? Because people fake the disorder. If people did not fake the disorder, people with the disorder would be able to get the help they need much more easily. People who have ADHD suffer because people who don't have ADHD fake the disorder.

It's a win for me

I suspect you may be underestimating the danger you put yourself in when you abuse drugs. It may be a win in the short term, but not so much in the long term.

it's a win for him because I have to pay him

It is not a win for him because 1) He probably has a moral compass and does his job so that he can help people, not just so that he can get money. Him giving you Adderall is a loss for him, because giving you a false diagnosis and drugs you don't need will cause you harm in the long run, and doctors most certainly do not get into the profession to cause people harm. 2) If he has professional reason to believe you do not have ADHD, then he could (probably) potentially face extremely harsh legal ramifications for falsely diagnosing you against his better judgement and giving you potentially harmful drugs.

I think what I did was a lapse in judgement because I only did it because a guy claimed to have one of the finals for a class, and he wouldn't sell it to me.

Here's what this statement sounds like to me: I did something immoral because I had a lapse of judgement. But I only had this lapse of judgement because I couldn't do something else that was immoral. Again, I really am not very knowledgeable about ASPD, but this statement makes a really good case against your argument that you are a compassionate, empathetic individual. I'm not saying that you are never compassionate or empathetic, but it seems to me that you are somewhat more shortsighted than the average person as to the effect your actions have on others.

To be honest, I think you should listen to what your doctor says. People (not just you, but everybody) tend to not be able to not be able to look at themselves objectively. Your doctor is a professional and he can look at your personality from a completely objective stance. He has no motivation to lie, and every motivation to be as honest as possible to you. Yes, there is always the chance he may be wrong. But even if he is, he has offered you some useful insight.

I don't think anyone likes being accused of being a sociopath. I think one thing to keep in mind is that no one is "all good" or "all bad." Everyone is a bit of both. There is a lot of stigma attached to the diagnosis he gave you, and there are people who might think that having that diagnosis makes you a "bad" person. There are some ways in which you are a "good" person (you do community service, you avoid fights) and there are some ways in which you are a "bad" person (you tried to fake ADHD for drugs, you'd buy a final for a class if given the chance).

Your own lack of objectivity may be making it easy for you to see the ways in which you are "good" but hard for you to see the ways in which you lack empathy. After all, if you don't have it, how would you know what isn't there? Again, I'm not saying that you completely lack empathy, but that based on what I've read, it doesn't seem to be your strong suit.

My advice is to come to terms with the fact that your doctor is not going to change his diagnosis and to maybe find some people (friends? therapist?) who can help you learn to make decisions that are more considerate of other people.