Accidentally deleted my entire music library with erase & sync. Any way to recover the music?

The other night I installed iTunes, after having it uninstalled for a number of months prior. Without thinking, I must have clicked "Yes" when prompted with whether I would like to erase and sync my device to this computer, as I woke up the next morning to find that all of my music (around 500 songs) had been removed.

Now the thing is, a lot of my music was not purchased from the iTunes store, but from various other retailers (depended on the price of the song); so therefore, I cannot simply re-download them from my iTunes purchases.

The other thing I don't get is why I was prompted with the erase and sync, because this is the same computer I have always connected my device to in regards to iTunes. The only thing that has changed is that the last time I had iTunes installed was on Windows 8.0, but since then have upgraded to Windows 10.0.

Is there any way to recover this music? It would take so long, and pretty much impossible, to remember and re-collect all of the songs... It is irritating as I've spent so long over the years acquiring all of these songs for them to just be gone. Is there any third party recovery software or anything I can do?

Please guys, any help is appreciated! Thanks