Fraud

Impostor syndrome is the number 1 enemy of transgender people and the older you currently are now the more it will plague you. Having grown up under a very rigid binary will only make things worse. 

I am not sure it ever goes away but it can be mitigated into becoming a low hum which sometimes rears its head. Under its spell your brain says "you are a fraud, you don't belong here and everyone can tell" 

Ask a gender therapist and they will tell you this is the most common issue with their patients; including those who fly perfectly well under the societal radar. The reason is that it doesn't matter how well you blend in but what your psychology tells you about yourself that governs everything about you. 

The good news is that everyone walks around with insecurities we can't see. They wear a mask that they operate with but once you get behind it there is an individual who is unsure about many things; unless of course they are a narcissist which most people aren't. 

One day I stopped trying to figure out what people were thinking about me as I was speaking to them and it made all the difference in the world. Their energy towards me improved greatly as did my sense of confidence and calm.

If all goes well one day we realize we aren't a phony but are simply uniquely ourselves.