iPhone 4S running iOS 6 skips songs

Hello all,

     This whole support site is new to me, so I'm sorry if I put this problem in the wrong place.  About a month ago when iOS 6 was releasedI updated my iPhone 4S.  Now a lot of my songs skip automatically.  Shake to shuffle is off, but I don't know about iTunes Match.  I've restored my phone twice, resetted and restarted it, but to no avail.  I also noticed somethin peculiar;  when I'm in iTunes (latest version for PC), at the bottom of my music library it says I have 6.18 GB worth of music, but when I sync my iPhone, on the iPhone information page the storage bars tell me that I have 12.8 GB worth of audio on my phone.  How could this be?  Again, sorry if this is in the wrong place and I'm sorry that this was really two questions.