Advice please help, duck eggs

[Gembo100]

I have a duck egg around 22/23 days - I wasnt convinced there was life - I candeled it and saw that a beak shape in the air sac quite clearly but no movement still, still nothing so this morning I candeled again and the beak shadow was not visable the air sac looked bigger too (may be my imagination) is this a good sign, is the duck just shuffling around - should I leave it alone now or keep checking?
I've never done this before any advice will be great - it was an abondoned egg by hen is sitting on

 

[luvmypets]

Let it go to the hatch.. I was convinced my three eggs were dead and then