3 weeks post-op, one ear sticks out more than the other after ear surgery? Is this swelling?

It could easily be swelling but some asymmetry is not that unusual after otoplasty. Its quite hard to see both ears in a person unless they are staring directly forward so don't worry about it too much. I am sure what you have is an improvement over where you started. Consider the potential additional complications in revision surgery if that is what is needed and wait at least 3-6 months before you consider that an option. Hope that helps. Adam Goodwin

3 weeks is too early to be sure about the end result. I would express your concerns to your PS. Certainly swelling can cause the ear to be more prominent following surgery so it possible that the ear will improve if it is just swelling. However bleeding with a haematoma can also cause prominence and this may be better drained. 
In the absence of a haematoma I would generally wait several months before assessing the final result.