What's causing my philtrum to be asymmetrical? Is it because my lips are crooked or is it because my septum is crooked?

Well, an asymmetric philtrum can often be due to a crooked septum (as you mentioned). Sometimes however it is a lack of symmetry between the two sides of the face. Your nose may be straight but your teeth off to one side. We cannot tell without an open mouth (at rest) photograph.Often these problems can be corrected, though it depends upon the cause.

Hi there and thank you for your interest. The Philtrum is the indentation between the nose and your upper lip. It is created by the muscle that runs like a circle around your mouth. In the philtrum the muscle fibres running from left and right cross each other, which creates the indentation in the middle, and insert into your skin, which creates the strip-like elevation we call philtre columns. There are various reasons for asymmetries. You have already pointed out very common reasons for a deviated philtrum. Other reasons could be: asymmetrical thickness of muscle-fibres, asymmetrical insertion into the skin, asymmetry of teeth or bony structures. 
In order to identify the reason(s) a thorough examination is required. Any therapeutical option will be based on a precise diagnosis. 

Good luck!

An in person consultation is obviously necessary. From your pics it appears relatively straight to me. But you are correct in that both crooked lips and or a crooked nose/septum could affect philtrum position along with a facial nerve paralysis.