How do I know if I have a valid medical malpractice case

My son is 3 years old. He was born with low blood sugar so a catheter was placed in his belly button to give glucose. First he suffered MRSA in that sight in the hospital. Now he has PVT (Portal vein thrombosis) because he was never followed up on for the catheter. I begged his pediatrician several times a week to find out what was wrong with my child because he vomited on a daily basis plus he had every sign for liver disease but she refused to believe anything was wrong with him saying that all the symptoms he was showing were normal and just trying to give him anti-vomiting meds. This went on for a year. I even took my son to multiple different emergency rooms trying to get more opinions and they all said the same thing... He was fine.. My son's belly looked like he was 9 months pregnant and we kept being told nothing was out of the ordinary. Finally after going through this for a year and begging everyone and anyone for help there was a scheduling error and we had to see another pediatrician. She took one look at my son and immediately took action and requested blood work to start. Turned out my son's hemoglobin level was at a CRITICAL low of 3... He needed emergency blood transfusions and then the search began to find out what was causing him to be so extremely sick. Finally after months of tests we determined that he had a blood clot in his portal vein that because it went untreated for so long was now not able to be removed. He now is on blood pressure medicine for the rest of his life and will need to follow up with his gastroenterologist and hematologist regularly. He also sees a liver specialist at UCLA because ultimately he will need surgeries to prolong the now inevitable liver damage. Myself and his father have missed so much work since this has begun and will continue to do so as he needs follow ups regularly. He is also, according to his gastroenterologist, a huge bleeding risk patient because he has esophageal varices that occurred because of the clot. At any time one could rupture and he would need emergency surgery or he could bleed to death. I cannot afford to stay home with him so it is a constant struggle to go to work hoping and praying that nothing happens while we are away. I really need help to have this case recognized so that the pediatrician my son had cannot let this happen to another child. She said that she just never heard of this kind of thing happening to a child so she didn't bother doing research. Those were her own words when I took him back to see her after his blood levels were brought back to normal, his skin tone was returning to normal and the fluid in his belly was going away. Please help. My son will now need medical treatment for the rest of his live because no one bothered to review and research his medical condition. Thank you