Hi Piggychunk
First off I'm sending you a soothing cup of virtual tea
.
Look you've had a move, probably losing a lot of your support network.
Second, you probably knew the drill at the old school and have now gone right back to square 1 - being the new Mum, not knowing where to go, the system, etc...
Third - yes, he's your baby and it means that his toddler years are coming to an end - he's growing up.
Fourth - the first day at school is always hardest (I was worried for my Y3 and Y5 DDs last week on their first day - it's what Mum's do).
I suspect you've been positive, strong and optimistic about moving and school all summer and now that nothing can be done and he's off on his first day, you probably just had a bit of a crack in the veneer of keeping it smooth sailing for your DC.
You'll be heading off to pick him up soon. So have that cup of tea and maybe something sweet (for the energy) and my advice is make it a slow walk home (maybe by the park) if the weather's good and find out about his first day. I'm sure he'll be excited and hopefully likes his teacher and has made a few friends.
It will be easier tomorrow, and even easier in the coming days...
Hang in there!