Congrats!
It feels good to do something for yourself. There is often anxiety that builds in the waiting period, even to get your scripts filled. It should come as little to no surprise that the first things you will tend to notice are relief and happiness, many describe it as a calmness.
As to weather or not that is the meds... who cares? Enjoy it!
You will probably be hyper sensitive for the next while, as you look into yourself and try to determine if anything has changed. That can take a while to settle down.
I suggest you make a journal entry, take a selfie, and measure yourself, to mark this occasion.

Ask anything, you know we are here for you. Also, consider reviewing some old threads. I swear they can read like entirely new topics when you are actually on HRT rather than imagining what it will be like.
Get ready to trade the morning salute for headlights!