To ask what ‘it’s just you’ means

[Watermelonburst]

I have autism. I’m kind of flirting with an old flame over message.

He always says ‘it’s just you’ but I don’t get it.

Please could anyone kind of explain.

I think he's saying he didn't make the first move because "it's just you" ie you make him nervous because he fancies you not because he doesn't like you

Hun, the majority of the time when someone says that it means
that’s Just the way you are, your way of being.

now the actual meaning depends on the context, so maybe he’s saying “that’s how you are and it’s lovely”, or maybe “you should accept your little quirks and don’t worry about it”, or “that’s how I expect you to react, it’s so you”

Whatever his meaning OP, he's clearly keen. Let us know how things progress!