I'm the same way, always had an interest in females since kindergarten, had 1 week-long 'relationship' in 8th grade and many many many crushes. I had an SED teacher in the 11th grade who first came off like one of the 'bros' but began targeting me for sarcastic gay slurs that seriously messed up my program. I've only had that light bulb go off in the last few months; I believe it's even possible he could have frightened away a couple girls I was wanting to get to know.
Anyway, sorry to see the stereotyping still goes on. When everyone else was gearing up for the prom I was in the thick of a tropical fish aquarium obsession, hormones hadn't kicked in yet and I just couldn't see what the big deal was.
As far as this classmate, odds are he wasn't an aspie or his curiosity would have driven him to ask you himself. #2, what business is it of his? Thirdly, unless you 'were' and he 'was' and there was a mutual connection, he asked a pointless question that has a pointless answer which benefits noone
And so, the vast majority of my gay acquaintances and kin have all known they were that way at an early age, in particular an uncle had a certain nickname for himself before he reached middle school but he didn't come out fully until my grandpa died
Anyway it's pretty much a universal aspie thing to be misunderstood, and one's preferences or lack thereof are just another aspect. If being alone so much bothers you, do what you are able to change it. If you're fine with it, don't let someone else's standards influence you. But just like with me, Ms Right isn't just going to knock on my door someday, so I try to at least make myself visible to any potentials
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Let's go on out and take a moped ride, and all your friends will thing your brain is fried, but you can't live your life too dirty, 'cause in the the end you're born to go 30