Had a small serving size of sugar free candy almost 24 hours ago and I've been having horrible pains in my stomach and esophagus should I go to ER?!?

Abdominal pain. Unbearable abdominal pain should be investigated promptly. I doubt your symptoms are related to the piece of candy that you ingested. You are on high risk meds also including opiates and benzodiazepines and that' s why seeking immediate medical attention is critical.