Spend ten minutes with me in person and you might mistake me for being Neurotypical. Ten hours...that's another matter.
1. In the simplest way to explain it, being overwhelmed/overloaded evokes a
flight/fight response from me. If I begin to sense I'm going to experience a shutdown, the first thing I do is physically remove myself from humanity in as much as is possible.
2. In a shutdown situation (I'm not prone to meltdowns) apart from not interacting with anyone I'm apt to be in an environment that is as quiet as is possible...where the loudest noise may be my own thoughts and heartbeat and little else.
3. That's the saddest part of my autism. Yes, I can miss people terribly. But I can also crave solitude to the point of pushing away those people I care about. It's not logical. It just happens. So "rationing" my time with people I care about deeply helps me to sustain my sanity as well as whatever relationship I might have with someone.
4. Interesting question. I don't think this is related to autism, but I'm not really sure. Few people here seem to share this particular trait. That is, I don't experience jealousy or envy like most people appear to. And yes, it can be problematic at times.
5. Crowded places? Oh my. Probably the easiest way for me to slowly and quietly get very tense. To that point where my fight/flight response kicks in. The classic scenario- a crowded shopping mall at Christmas. After so many minutes of people rushing all around me, I became tense, felt my heart rate increase...and nauseous. Had to bail and I did. Sat in my car for a half hour or so to recover. The resolved to shop at less crowded places where total strangers didn't so easily violate my personal space.
OCD? I was formally diagnosed with that and chronic clinical depression in 1982. Only to realize decades later that both are comorbid to my autism. Oh yes...you should see my immediate environment. Where everything has its place..relative to being parallel or perpendicular to everything else. With extreme attention to detail. It wears me out. And then I also have other aspects of OCD considerably more bizarre that I manage to keep to myself. Rituals of constantly having to check locks...alarms that sort of thing. And occasional thoughts of terrible consequences for benign things. Like superstition on steroids. Utterly illogical, yet I cannot seem to push such thoughts out of my head.
To let someone into my life on an intimate level...they might eventually think I was stark-raving mad.