Q: Username changed into losing everything, how do I get my stuff back?

So I decided to change my username on my mac, the one that comes up on the top right hand corner of your screen near the clock.

Anyway I googled the instructions it said to change it through advanced options and I did and now I can't access my files from my old username.

I know it gave me a warning prior and I followed all the correct instructions but now everything's gone and I'm freaking out!

I can see through the 'about this mac' that the files are existing somewhere through the memory drive but I need it to convey on my new username.

Someone help!!