I don't understand why people tend to have these out of character, unprovoked hostile moments with me

Sometimes it's as if there's a target painted on my forehead and I'm unable to see it. I notice plenty of otherwise seemingly cool, supportive people show their darker side with me and almost drop all tact and just go at it.

I don't know if I say things that trigger people or do something off-putting that I'm not aware of but I feel easily excluded in social groups and as a result of past negative experiences I have to be extremely cautious when meeting new people.

There's almost a sense of discrimination for no particular reason I'm facing. A more concrete example is an otherwise nice and likeable girl refusing to go out with me (even platonically) because in her words I have the social skills of a kindergartener. I called her out on it and she half-assedly apologized for being too harsh and just said it's because of a "difference in energy" that unsettled her.

Is being socially awkward and depressed enough to warrant this kind of treatment from others or is there more to the story that I'm just not aware of? What should I even do about it?