I have a question about self defense and owning a gun?

It depends on which state you live in. Texas and Arizona have laws that highly protect the rights of property owners in these situations. However, in most states, as a general rule, if the force that you are using is disproportionate to the force that you are being threatened with (i.e., someone "attacks" you with their fists, and you respond with a gun), self-defense is not going to work out for you as a defense. You also should keep in mind that even if you think you were acting in self-defense, that's still all it is -- a defense -- and you're probably still going to have to sit through a trial. Not worth it.