By "I don't believe in UFO's" I will assume you mean "I don't believe that UFO's are alien spacecraft".
UFO's themselves are Unidentified Flying Objects, and they do exist (I've seen many of them myself). Likewise with crop circles, they exist, but I do not believe they have a paranormal or extraterrestrial origin.
UFO's themselves are Unidentified Flying Objects, and they do exist (I've seen many of them myself). Likewise with crop circles, they exist, but I do not believe they have a paranormal or extraterrestrial origin.