diagnosing autism in toddlers

[jellybaby01]

I'm not so much worried that my little boy could have autism/ADHD, I'm more worried about not being taken seriously.
A little brief: He's 2 years 8 months, he's non-verbal (although said mum for first time the other day, yes I cried lol), thrill/sensory seeker, licks everything/ puts things in the mouth still, sensory issues with some textures and food, he has 'Andy's coming' tantrums I like to call them as they are unpredictable, he can be very aggressive at times, hates other children in his space at mum and baby groups and soft play if another child plays with 'his' toys or wants to share, he will hit them pull their hair push them etc, he can parallel play children sometimes but will only really connect if they will play chase with him. Socially except the aggression nursery backs me on that. At nursery he can only join in group activities if he has a 1:1 with a adult else he becomes very overwhelmed. Used to walk on tip toes all the time, and turn things upside down however now he is growing out of that. Behaviour can be unpredictable. Responds to his name half of the time. If he's not in a highchair then he won't eat meals. Bed times are a nightmare even with a set routine we've had for months, he can't settle. When his routine changes he gets upset - example: he has limited diet and nursery are helping me with this, normally he has soft cheese sandwiches, I sent him with chicken paste, he sat there and cried and refused to eat anything rest of the day.

I am more then aware, a lot of this can purely be down to the fact he can not communicate his needs, however I personally feel there is a little more to it then that. I just feel that I'm not taking seriously, speech and language have been useless in both sessions. She also said nothing could be wrong as he can keep eye contact most of the time, and shares her toys. I said that's unfair judgement to make in a 30 minute session (we've had two different SALTs).

How can I be taken seriously? I know he's young, I do 1:1 with children who was late diagnosed and find it hard in school, most because their parents weren't taken seriously at 2/3, and I fear this will happen to my son. Any advice is welcome, thankyou!

Well, the fact that the Nursery staff see the same behaviour - and clearly know him well should be evidence enough for a referral.
Where I am, the Nursery would make the referral. Why haven't they done so ?
Obviously I've never met your dc, and nobody can diagnose anything over the internet, even if they were a Paediatrician, but there are enough things in your description to warrant a referral for assessment.

Who isn't taking you seriously ? Have you asked HV? / GP ? Nursery SENCo to refer in for further assessment ?

@BackforGood my HV referred him for speech and language, and community paediatrics, I've sent her my observations and she's gonna try fast track a appointment.
Speech and language passed us onto preschool complex needs team, who told me "in the 45 minutes I've known him, I don't see any of your concerns I can get eye contact, and he can show me my toys, I have no concerns and there's no point in a referral" it just made me really upset and nervous that my little boy won't get any help :/
Except for aggression he mirrors in nursery. There's no reason for him to not speaking, like physically cause I've been doctors and such for it. I'm just a loss and I feel being on my own won't help, as a lot of people advice to take the "baby daddy" as they are listened to more, but I don't have that luxury