Hey newgrounders!

I just rebuilt a melody that I think is popular. I play this very often on the piano I have at home so I decided to upload it on newgrounds and I hope anybody can tell me where it's from! ;)

Please help me, is this already existing? Or is it really just something I had in my head and it's originally from me? I named the melody "Popular Melody?". Just listen to it and help me to find out where it's from!

Greets, ttk.