Remember you aren't trying to please your English teacher. What you are trying to do is get your particular story across. Grammar helps you do this by making sure the words and sentences make sense. It all adds to the larger picture. Now you may have a narrator's voice who doesn't use proper grammar. Use it to your advantage. Remember Mark Twain's Huck Finn? OR more recently, Kathryn Stockett's The Help? Both stories use imperfect grammar to create narrator voices that engage and charm the reader. One caution, if it's your narrator's voice, it's good, but if it's the author's narration in poor grammar, not so good.
When in doubt, ask an expert, someone you respect who has the knowledge of good grammar, and if you are still confused, don't forget there are plenty of grammar books out there to assist you polish up your diamond in the rough.