Contractions?

Hi ladies. How can you tell if you’re having contractions, Braxton Hicks, or if it’s just the baby’s position? I have intense upper abdominal pain that varies in intensity. I can feel it throughout my stomach and my back. There’s no pattern it’s just painful and repositioning doesn’t help. I do plan on calling my doctor. I’m just asking for opinions. I never really felt painful contractions with my first so I have no clue what it would even feel like. Thanks ladies.