Dear White witch
I want to do magic but I am deathly afraid of saying something wrong and having something backfire. I wish no one any harm, but I feel there is evil around me. My dad once told me that when he was younger he was curious about magic and decided to cast a spell, he says he thinks he summoned a demon, and I feel part of that demon has passed onto me. Sometimes I hear voices all around the room. I have horrible agonizing dreams, and have insomnia because of it, I'm asking for any advice on what I have told you. -Wyatt
If you cast a spell and you do not fuse negative energies into it, there is no reason it should backfire on you. If you mess up the spell, just restart it. Also, if you don't get it on the first try, it's never a bad idea to try it again.
As for the other part of your post, I recommend some protection spells. You can also meditate and build shields around yourself to ward off negative energies.