Ok I had a similar problem. My songs were getting repeated everytime I restarted the phone. I had about 400 songs and soon the music app was so huge with over 1800+ songs, I could no longer adjust. So I bought a card adapter and formatted the hell out of it. 3-4 times in different settings. Still same issue. But then it became worse. The phone would not recognize any files (music, picture or videos) and treat them as "other".
Today I did a hard reset and everything fine now. I hope this helps. But remember to backup your files and settings..