Autism is a spectrum, if you have to think about social interactions, you probably are on it. It doesn't mean you don't have empathy, or that you aren't a functioning human (That's why i really dislike people using "High-functioning autism"), but sometimes you have less to hide than other autists, or you're thinking quick enough to hide it better than your peers.

The fist hint for me was the psychologist who taught me how to lie (or rather, explained to me social interactions, as i did not care about it at the time), and that's as clear as it can be, but sometimes its only weird result on IQ tests: if you moved countries if often don't mean anything, but if you did not and you scores are not homogeneous accross the tests, like 4 in the high 130 and one in the low 90s, you're probably on the spectrum too.