Good point. Clark seems to assume that all the things Lex suspects about him are only hunches that he THINKS are true. But in reality, with all the things he's seen and experienced since coming to Smallville and meeing Clark, he KNOWS that he hit Clark at 60 miles an hour. He KNOWS that Clark was in the cave. So he KNEW Clark would save Lana and therefore nothing would happen to her. But of course he doesn't know Clark has lost his powers.
And I kinda agree with DarkSkywalker, Clark's whining is a bit hypocritical. Even when it's something as low key as Lex asking Clark in the eps Ryan, if he thinks it's possible Ryan has special abilities. Clark immediately accuses him of trying to exploit Ryan. Trying to find the truth and exploiting are two different things. In reality Lex is what Chloe used to be except with more resources. Of course now it's entirely different, now he is trying to exploit Clark. But in the past, even in Season 4, all of his digging he kept to himself. HE wanted to know Clark's secret, but he never wanted anyone else to know. Like how he became angry with Roger Nixon or Perry White or that FBI agent when they tried to investigate. So if Clark had told him then Lex would've kept it a secret I think.
And remember what even Clark's parents said, with everything that has happened to Lex you can't blame him for trying to find the truth. This is why I don't like how they're handling Lex's turn to the dark side. I want them to show us SOMETHING ELSE than Lex trying to find out Clark's secret, in order to make us believe he is someone we should hate.