You have facing pages, so you should set up your document as document with facing pages.
You should have done it with New document but you can change it with File > Document Setup.
You will have to change your master to 2 pages and to allow to shuffle the pages.
Shifting pages are shifted when you use the page tool. It can happen more easily with non facing pages.
Was there a specific reason, why you choose not to use facing pages at the first place?
With the page tool you can shift pages.
With your answer I now think I know what I have done. I did choose facing pages, and it is checked in document set up, however I think I have accidentally used the 'page tool' at some stage. I remember grabbing it by mistake, I am not certain how to fix it as this tool is new to me, but I can do some research on it, thank you so much for your help, it is very much appreciated.
Grab it again and drag it to the correct position. It is similar to use as the selection tool, but you don't move items, you move pages.
Fixed with no problem at all, thanks for your help.