My son is 6 years old. He has a diagnosis of Social Pragmatic Communicative Disorder (which is a lot like Aspergers though technically he is not on the Autism Spectrum, so I usually just tell people that he has Aspergers) and ADHD.
When my son is having a meltdown at a restaurant, store or other public place, I wish people would just leave me alone and not try to help. I'm sorry that he might yell or scream. I'm sorry that he might lie down of the floor like a 2 year old and refuse to get up. I'm sorry that that might effect someone else's experience. I am learning, too. I am learning to have patience, to be even more consistent, to remain calm but not back down whenever possible so that he doesn't learn that throwing a tantrum will allow him to get his way. I am still learning.
When people try to help, they actually make the situation worse. They draw more attention to my son, which causes him to get more upset. I do realize their intention is good, but it does not help at all!
On the other hand, I need to learn how to deal with people when they do try to help or just when the stare. I need to remind myself that they really have no way of understanding and that I really am doing all that I can and doing it to the best of my ability. I need to remind myself that it doesn't matter what people think. I know that I am doing all I can for my son. It would be nice of others could be more understanding, but that's just not always going to happen and I can't afford to spend any energy on them. It takes a lot of energy to be a good mom to my son and to be a good mom to my older son, who also deserves my love and attention. They need my energy. I do not need to spend energy on bystanders.
Try not to give too much thought to those who question you. You know that you are doing all you can do and you are working with the doctors/teachers/specialists, etc. That's you can do.
I do find it's helpful to just be upfront about our son. I tell his teachers, other parents, scout leader, etc, about his diagnosis. Knowledge is power. I know some people prefer to be private. I'd rather be open. A family we are good friends with have a daughter with some special needs. We don't really know the specifics, because they prefer to keep it private. My husband has commented (to me) many times and asked why they won't try to help her. I had to remind him that just because they don't report to him the specifics doesn't mean they aren't doing anything. (Where do people get that idea?) They want to keep it private. I'm ok with being completely open. I'm sure some people find it odd, but I like others knowing that our son has a diagnosis (no, we are not ignoring his needs), and we are doing everything we can.
ETA - Thanks, Julie S. You are absolutely right. I will practice smiling and saying, "Thank you, but I've got this." I know people mean well.
Patty K, yep, some people will choose to keep things private. I find it very helpful to not be private, but that's what works for me. My son is very loud and can definitely make a scene, so I see absolutely no advantage to keeping his diagnosis private. Each family has to do what works for them.