@redz16 I have a son who was exactly like this. Please find a neuropsychologist and don’t just take him to his regular doctor - his pediatrician should refer out to a psychologist based on your initial concerns but a regular psychologist can’t diagnose. It has to be a psychologist who is a diagnostician or a neuropsychologist can properly diagnose whatever is on. They will want to rule out autism and potential abuse, trauma, etc. He has to be 6 to qualify for the DMDD diagnosis but he sounds exactly like my son so learning about it can help. DMDD is a relatively new disorder as of 2013.
My son has DMDD and ADHD (very common to have both or to have DMDD and Austim or all 3). With the right meds (Matthews Protocol), if it really is DMDD, he can live a normal life and people won’t even know he has a neurological condition. At age 5 my son was kicked out of preschool and ended up in a psych program - we didn’t get the DMDD diagnosis until age 6 though. Please watch this video (it’s 1 of 5) on the disorder.
(Also, if this behavior happened almost overnight in conjunction with an illness, it is a possibility that it is PANDAS.) If it ends up being DMDD, stimulants and antipsychotics make them worse but it’s always the first go-to for docs unfamiliar with the diagnosis. If after watching the videos, you think it’s a possibility your son has this disorder, I have a list of doctors familiar with it and how to medicate it, let me know.
No matter what diagnosis he has, he’ll need to be evaluated for assistance in school when he goes to Kindergarten also or he will be punished for his behavior which is not right if he has a neurological condition. With a neuropsych evaluation, you can take this report to the school and request an ARD meeting (usually has to be in writing to administration and the SPED person) to set up an IEP. The neuropsych evaluation can include his educational needs that will qualify him for the IEP. A 504 won’t be enough if your son’s behavior continues in Kindergarten.
Hope you find some answers soon! If you’d like further resources, let me know. I’m writing a book on the disorder currently.