I would start by speaking to the GP. You can book an appointment alone or if you have someone with you so DS is only present for part of the appointment you can do that or you can write some notes to give to the GP if you don’t want to speak in front of DS.
In the UK, it is very, very unusual to get an assessment for ADHD at 4. You could request a referral to a neurodevelopmental paed though for a wider more general overview.
In some areas there are drop in sessions with OT and/or SALT. If your area has them, it is worth attending.
OT will help. Not all ICBs commission sensory OT on the NHS, but either way I think a referral it is a good idea.
What support did the preschool provide? Did they refer to &/or consult any outside agencies?
Have you spoken to the SENCO at the school DS will be attending? Has he had an enhanced transition?
You can request an EHCNA yourself. On their website, IPSEA has a model letter you can use.
When you say DS is given consequences, what do you mean? I’m not asking in a way to say you need to give consequences/more consequences and criticise you. I’m asking because some DC with additional needs need a different approach and typical consequences can backfire and ramp up behaviour.
Some people find the Out of Sync Child book helpful. There is a ‘has fun’ version too. You might also want to try some of the ideas in this booklet. The Occuplaytional Therapist has some useful resources too.
How are DS’s sleep and eating?