my itunes won't connect to the apple store or let me download any new music?

i used to just download music from a youtube to mp3 converter website and i would just click and drag the file into my itunes and then sync and then the song would be on my phone/itunes; but now whenever i try to do that it says "file does not seem to be a valid podcast URL. please check that you have entered the correct URL and try again." i tried downloading music from other websites that i know always work, but the same message pops up everytime. I also can't connect to the itunes store or check for an update. my itunes has been doing these things for weeks and i don't know what to do to fix it.