Nether Portal Bug

I made my first nether portal on the world and decided to go through it to see if I live near a nether fortress and went back through my portal...

What I expected to happen was...:

To go back to my original nether portal to go back to my base

What actually happened was...:
I actually spawned about 130 blocks away from my original portal 

Steps to Reproduce:
1. no clue, but again that was my very first nether portal that i made on that single player world
2. Maybe it's because I live about 13k blocks away from spawn idk
3. ...