Hey OP - I remember your previous thread very well. I commented last time to say we're house hunting and I am extremely anxious too as I don't cope well with change.
I get it, I really do. But I think in reality you would have felt like this about any move. You loved your previous neighbours and your area, but the house was too small. You couldn't have stayed - but there's nothing that would have been an acceptable replacement for that familiarity.
Gently, gently. Over time this house will start to feel more "yours". It's such early days.
When I get anxious, I remember reading a thing that said "you have everything you need right there". You have your family with you. Just refocusing on the important things. Don't allow yourself to dwell. It's so easy to get sucked back in when you're feeling insecure and anxious.
You need to make this house feel exciting. Warmer weather and brighter days will help SO much. In the meantime, great advice re ditching RM and replacing it with Pinterest. Throw that house hunting energy into creating a really special space.
And set a time limit. If in say, 18 months, you still desperately unhappy then you can move again. Your child will absolutely be fine to move at that age, they're incredibly resilient and lots of DC move schools etc when they're very young with zero lasting effects.
Give yourself and the house time. After a summer spent enjoying your new, beautiful garden and exploring the area you could feel very differently.
You're just missing the familiarity. Nothing more. You've got this.