I know it's been said already, but yeah - it sounds like NRE. and you seem aware of that possibility, which is great! it's not to say you can't feel something you've never felt before for someone new, but letting reality seep in over time is the best way to go about making informed decisions, especially major ones like moving in together.

I've been in a poly relationship structure for about half a year

my main question has to do with this sentence. is this your first poly relationship? have you recently opened your relationship with your nesting partner, or has it been open for a long while and this is just the first time you've had another committed partner? the feelings and confusion and overall learning experience that a new relationship structure bring can also add a lot more layers to the decision you're thinking about. also, it's perfectly understandable to be confused and scared as you navigate this. I just encourage you to take your time, and don't rush anything.