Abdomen exercises. Keep in mind that no matter what you think, you are beautiful and no one can tell you otherwise. I don't think you should try to change yourself unless YOU have a problem with it. I understand fully.
Running takes a LOT of core muscle so yes, it will. You'll have to increase your mileage though. I'm a collegiate runner on scholarship and have trained and been running since I was in 7th grade and am a med student, I know what I'm talking about. You cannot depend solely on running to flatten your tummy. Do various workouts to keep a balance; life is ALL about balance (don't stretch cold muscles that is stupid-make sure to do a small warmup THEN stretch. eat a lemon after workouts, to help with lactic acid)