What can I do if my child was misdiagnosed by a doctor?

My child was diagnosed with a double ear infection at 7:30 am. At 10:00 am, the doctor said there was no sign of ear infection. However, I told the doctor he was complaining of a belly ache not his ears. Antibiotics were given which made his belly ache even worse. My child had to be in constant pain when the first step that should have been taken was an x-ray which he didn’t receive until a third visit to a separate ER. He in the end was misdiagnosed and rushed out of the first visit at a separate hospitals ER.