The more I think about it, the more I come to the conclusion that being Tony Stark is suffering. Genuinely suffering. Mostly because I don't think he actually enjoys anything anymore. He's long past the stage of being an Adventurer, which is why I thought Civil War wasn't such a big departure from the character; he grew up. So the things that used to make him feel content, suddenly don't. All the friends and lovers have betrayed him, or been hurt by him, too many times for them to have the same connection again.
Ultimately I think the problem with Stark is that he needs companionship, because that's who he is. His childhood wasn't particularly sad or extreme; Howard was a bit of a Macho Man, which isn't uncommon. Thus he stuck to his mother's dresses too ften. Eventually he grew up and put on a mask. Lots of people do it, it's no biggie. But he never really outgrew the "broken little boy"; he remained emotionally stunted, even if he grew intellectually. It's evident, since the moment a relationship ends, he looks for another. And every time he's in one, he doesn't cheat, like one would think. He just wants that old, romantic love.
But next to that, where I think the big problem lies, is that he's ultimately a bad guy. He knows that, and he's a softie, so he beats himself up for it. He tries to help, to protect, but at the same time he needs to be in total control. He needs to dictate, not every single thing, but the course. The contrast with say, Doom, is that the latter's a hypocrite, a totalitarian, and someone who can lie to himself. Stark can't, so when he makes the hard, cold, logical choices, he understands the moral implications. He doesn't want to micromanage everything, but he /needs/ to chart the course of the future, because he just knows /best/.
Ultimately, the real tragedy is that he's a man trapped in the past and the future. He has values of a more chivalrous era. Which is why he /needs/ to control the future.