Why do I sing good without music, but bad with music..?

I sing good without music, but as soon as I turn on the karaoke sing along I sound worse.. I always mess it up and I'm a tenor singer but the music makes me sing high notes which I struggle with. I'd really like to post me singing to my family and friends and stuff but it sounds boring without music and i'd actually really like to use music, but then I sound bad with music. Help?