Buddy, I am sorry yesterday was so hard, but it was NOT such a bad thing as it might seem.
This may sound strange, so bear with me, okay?
Have you ever wondered what WE seem like to Q? On some level he KNOWS that he has outbursts/meltdowns and isn't the same as most other people in any group he can see. He KNOWS he has hard days, but likely he does NOT think that you/adults do.
Yesterday he saw you having a hard day. NOT FUN for all involved, but IMPORTANT because times like this give him the info that other people struggle too. He may not be able to process this on a cognitive, talk it out level, but deep down it is there, and it is GOOD.
Can you imagine how awful it would feel to be the ONLY ONE who had bad days? Sure seems awful to me. So while you didn't handle things the best, and needed a break and triggered some stuff, you also showed your son that you are only human and make mistakes and that it is okay to make them because he still loves you and you still love him.
I remember when this was pointed out to me, I was upset because I didn't feel good and couldn't cope and triggered all the kids and myself and one in real life friend took my kids for a break and it ends up to be a memory I cherish. NOT because it was "fun" or even really 'good' , just because it was, and because I learned that sometimes it is more important to show the kids we are human than to have a good day.
Just a thought.