Yesterday my server crashed. Today I logged onto my server and I spawned in a different area, all my progress connected to my account is gone (achievements, inventory, xp, etc), and the server doesn't recognize my username when I do commands. I loaded a backup file from yesterday, but nothing. Everything I built is still up, though. I'm not sure how to recover my stuff.
On top of this, I noticed that everything in the nether has been reset as well.