"It’s difficult when it’s your first child and you don’t have a basis for comparison."
Absolutely. All I will say is that if your child is neurodivergent, it gets easier as your child gets older and you start to observe them with peers (eg at play dates, birthday parties) and see how they might struggle with some things that their peers don't.
At 4, everyone told me it was too soon and to wait and see. At 5, we paid for a private Occupational Therapy assessment - much cheaper than a full autism assessment and very helpful indeed. The report identified some sensory needs and made recommendations for things to do at home and school. By 6, I was more sure than ever that it was probably autism. Then I found out about Right to Choose, got the GP referral, and DS was assessed and diagnosed shortly before his 7th birthday.
I didn't think we would qualify for DLA - he is so-called "high functioning" (he masks his difficulties, he still has them, and needs a lot of support at home) - but we got DLA. I'm not convinced we would have got it if it hadn't been for the medical evidence ie the diagnostic report. It's supposed to be based on needs not diagnosis, but if your child masks and school insists they are fine, how are you supposed to evidence those needs if not with a diagnosis?
The DLA provides the option to pay for support that is not available on the NHS, private OT sessions for example, 1-2-1 swimming lessons because group lessons are too overwhelming, or specialist therapy for autistic children.