just curious/ future reference.

Ailee • 💜 02/13/15 😊 11/22/17 👶🏽
I have a couple pregnancy questions, I'm curious about some things.
When is the earliest a person will feel physical symptoms? What are they usually? 
On a different side of things, what could be the cause of a missed period besides being pregnant? 
If a period is late/ missed when is the best time to take a pregnancy test? Is there any difference between brands? 
That's all the questions I have at this point but I'm sure more will come up. Thanks!