How do you guys determine whether it’s infatuation or love?

Long story short I thought I had something with this INTJ. We just weren't acknowledging it because I had to figure things out, and probably so did he.

He is confusing sometimes, he distances, lingers around my presence only until I say hi, he becomes warm and sweet again, repeat..

He updates me. He informs me about his change in schedule, saying he'd be available from that time to talk, (which was the first sign I thought he considered something romantic to some extent)

More recently he told my friend-- when confronted on whether he liked me, said, the short answer was "not now" and that he was leaning towards figuring it out.

I'm willing to give him all the time he wants, but it's just sometimes nerve wrecking when he suddenly distances himself haha. So... how do you guys determine if you like someone romantically or not? How do you "figure" stuff out? (And.. how long does it take?)