Actually, I have to say that this time I'm feeling sorry for Clark.
Here he is, just feeling like he's finally getting control of his life when he accidently overhears a conversation. He finds out that he's a leech who's using Lois as crutch and that he's unable to sustain a lasting, meaningful relationship. I can't blame him for feeling a little taken aback. So he decides that he's not being fair to Lois and breaks off the relationship.
He may not be handling this in the best way, but I can totally understand why he's acting in this manner.
