Actually it makes more sense to me, to take it starting at 5mgs. That way the initial side effects wont be so horrible. If you arent having side effects, thats a good thing. 5mgs.... I don't know how effective that would be. It could still have some beneficial effects, id expect to wait at least a couple weeks before you really notice huge differences, but sometimes after only 1 week people notice a change or reduction in anxiety.
Whatever benefit it has, 5mg will probably be a lesser amount of benefit, but still something. Ultimately, your P-doc might have just been trying to minimize the side effects, because at 20mgs you would probably feel pretty horrible for the first 3-5 days after starting it. If you choose to up your dose, just do it slowly, very slowly, and be prepared for the short-lived increase/appearance of side effects, (sometimes they can hit people off guard, like me lol )
Because I know that here today, the Black Knights,..... will emerge victorious, once again.