Itunes wont add a track to existing album

I have several songs I've composed and created an album for them, I have just tried to add a new song I have just written to that album and even though I have put EXACTLY the same details i.e artist name and album name in the 'get info' field iTunes refuses to put my new track into the existing album, but instead creates a separate album for it. so infuriating!!

Anyone able to help?