I'm trying to write something in english but I don't really know how to do it correctly. He thinks that's the closest he'll ever get to being a heroine. Only, a few years later his boss calls him to his office with a new assignment and he starts doubting it. I don't mean it like "just a few years later" but like a "but" only I don't really want to have to use a "but". Does the comma shows that, what I'm trying to get?