My Lips Don't Close Naturally, What Can I Do? (photo)

I've had braces going on for 4-5 years now and I will be getting them off soon. For as long as I can remember my lips have never been able to naturally close but I blamed it on my overbite. My braces are coming off soon and I have a "perfect bite" now but my lips still don't close on their own. I questioned my orthodontist about this but she told me that my lips are just like that but I've done the research and I don't believe her. She says when my braces come off it'll help but I doubt it.