4 year old concerns

I am unsure of where to start. My little boy is definitely a spitball. I’m concerned he has ADHD and maybe some autistic tendencies. I made an appoint with his pediatrician but I don’t know if I need to skip the pediatrician and go to a behavior physiologist. He can’t sit still. His behavior has been awful. He doesn’t listen back talks. I have it because we get on to him more bad behavior then good. I am trying to be patient and understanding. His fat care calls me almost everyday complaining about him. It’s frustrating. I discipline and nothing is reinforcing his behavior.