> I have a question for former hikikomoris.
I could easily qualify for that category but I don't like the label.
> Generally I'm concerned about what people are saying.
The short answer is: Don't be concerned with what you think people are saying.
Longer answer:
If no one knows you at college (or knows anyone who knows you) they have no way of knowing what you've been doing for the last few years. So worrying about that is pointless.
If you've isolated yourself for a long period of time, your social skills have probably atrophied. You might be a little awkward or seem strange to some people.
If there's something about yourself you can readily change to make yourself more easily accepted, do it, but don't dwell on what you can't change.