My iTunes library music has been completely deleted and I can no longer add or remove music on my Iphone 4 from iTunes

So today when I plugged in my iphone 4 to my laptop I discovered that all my music had been deleted from my library. So then when I would download my music again and try adding music to my phone it wouldn't do it. I would drag a song over to the "on this phone" and onto "my iphone" where Im suppose to add music but it would not light up indicating that the song couldn't be added. So what I try to do next is sync what music I downloaded again into my library onto my phone and it seemed to have worked like that.

After that I tried deleting some music off of my phone and THAT wouldn't work either. I right clicked a song and discovered that there was no "delete" option. I tried it with all the other songs and it was all the same.

Sorry if this all seems confusing and long but please help. I'm also new to this apple discussion website so sorry if I post this in the wrong category lol