Why are songs being skipped on my iPhone 4S?

I've noticed it seems to be skipping only the songs that haven't been bought, songs that i downloaded off the internet. When i go on the music list and click on a song that wasn't bought, it shows up for a second and then skips. When i go back on my list of songs, i see that there's now a red circle with a square in it beside the song name and when i click on it, nothing happens. It won't let me listen to it at all. So then i exit out of the music app and when i open it back up again, i find that song has been deleted! Also, i don't know if this has anything to do with it, but it really seems like it does, last night i was trying to download music again and it showed up in my itunes library but when i would sync my phone, the songs would not transfer over. I tried to unplug and re-plug my phone into the computer and restart the computer and my phone but the songs still wouldn't transfer. And they were checked too! What should i do?

Because you don't understand how iTunes works.

That happens to many songs, it just wasn't downloaded correctly or something ****** up, so just try redownloading it and it should work just fine

Itunes only allows you to use legal music, ddepending on where you downloaded it, it may not be legal (to iTunes), you should buy the songs and avoid all the trouble. However, if you only want the music on your computer, or stream on your phone, usound.mobi is awesome.

hope this helps.