How to get back deleted Admin Files?

Hello! So about yesterday, I updated my (MacBook, 2009 ancient I know) from Mavericks to Yosemite

After it downloaded, on login screen was my old admin name user. I didn't mind it and thought it was a little bug so I signed in and decided To change my admin name. I guess I didn't see the "Warning" at the top but I'm not sure if that is the reason to my issue.

after I changed my admin name, I was told to restart and so I did. When it came back to login screen there was only guest account there?

so entered via Guest Account, System Preferences, Users and only Guest Account was on the list.

SO I made another Admin account, and went to /User. There was a folder of my initial admin name (.xx.) and it had everything there. Being quite ignorant I dragged the folder to my desktop but then it said I didnt have enough space.

ANd and so I went to System Preferences, Users/Accounts and changed settings to typing username and password on login.

I Logged out, and put in .xx. (My laptop username) In username and my password, and I got in BUT it was like a brand new screen (like how it would be when you make another account)

IT was the default background, none of my folders were on the desktop but I was in my main account. The weird thing was, was that in the top right hand corner it would've had my username beside the battery. However it was blank and when I clicked on it, only Guest user and my other admin was in the list.

i Went onto /Users and my .xx. folder and nothing was in there, my desktop folder/documents/pics Nothing except 3 folders that said Movies, Pictures and Music.

NOne of my stuff were in those three folders either.

I checked my trash bin and nothing was in there either. I'm afraid I have deleted all my things? Im not even sure how my admin got deleted in the first place.

please help me out as I'd like to retrieve back almost 3 years worth of memories.

thankyou so much.

P.s I haven't backed up with Time Machine so its really my loss :/