Why don’t some ER doctors take patients seriously?

Had a car accident and complained of abdominal pain after the accident and he said since your vital signs are fine you can go home but return if you experience vomiting. What if I have stomach bleed or something? How can they discharge me without an x ray? Also had pain in stomach when drinking water. Like whenever the water passes the esophagus into the stomach it hurts. Also to describe the accident I hit someone on the driver seat area side hard with the front right side of my car