@babybellx I'm glad the referrals are in place now but I also think you should look into changing nurseries. You need a supportive SENCO on board, even if you start the EHCP process yourself.
My DD is 4 months older than your DS and I first raised concerns with the health visitors over two years ago but it's been a long process to get anywhere. She's now waiting for an ASD assessment.
My GP requested a paediatrician referral and it was rejected twice. It was finally accepted the third time almost one year later. You will have to be really persistent in chasing referrals etc and I recommend starting a timeline of events/referrals so you have a record of what happened when - this will be helpful for the EHCP application and also the ASD assessment.
If you can afford it, look into private speech and language therapy and a private sensory OT assessment/ongoing occupational therapy. We recently had an assessment done and it was really insightful and lots of things were picked up that I hadn't noticed myself. The report included suggestions for home and also specific recommendations for school/nursery for the EHCP.
Look into applying for DLA if relevant, this can help fund anything private if you go down that route.
Start the EHCP process yourself, I did the same earlier this year. There's lot of helpful advice on the IPSEA and SOS SEN websites.
Join the EHCP support thread on the SEN board for advice, there are lots of knowledgeable posters on there - https://www.mumsnet.com/talk/special_educational_needs/5077140-ehcp-support-thread-no-3?page=9.
I also remember the initial shock and worry for the future. It's not an easy road to go down so remember to be kind to yourself and take things one step at a time.