I haven't worn my retainer for two months?

Yupp, if the retainer feels tight that means your teeth have shifted a tiny bit, even if you can't see it. Millimeters, I'm talking. So yeah you can wear it overnight and that will help shift them back into normal place so that the next time you wear it, won't be as tight.

yes of course,

i haven't worn mine in over a year !

the tightness is just the feeling of he teeth lightly shifted, although it is very minor so no need to worry !

in case you positioned on them for some nights in a row, your tooth will shift back into place after which you would be able to pass back to donning your retainers approximately as quickly as a week. i've got achieved this some circumstances.