I have trouble making eye contact, too. I wish there was less of a stigma attached to that. When I avoid looking into people’s eyes, I am not necessarily lying/shy/shifty.
I often go for walks with my sister. She’s much younger than I am, and I’m entirely comfortable in her presence. And yet, I frequently notice her searching for my eyes when I happen to glance in her direction.
It always catches me by surprise. Finding people’s eyes just doesn’t enter my mind, unless I’m greeting them, maybe. Even then, it’s social custom which makes me force myself to find other’s eyes, as opposed to an instinctual “pull” some people seem to benefit of.