Songs deleted from iPhone still appearing in iTunes

I added a couple hundred songs to my iPhone recently, but now I wanted to clean the library up of some songs I didn't want. I went on to the Music app and did the swipe left > delete thing for all the songs I didn't want, and they weren't appearing on my iPhone anymore, but when I went into iTunes and went on the "On this iPhone" tab, the songs that I deleted were still approving. I couldn't right-click delete, and I couldn't play them either. I want to wipe the library completely clean, but none of the songs are disappearing. Why is this happening, and how can I fix it?